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This method may use a proportional approach in considering the adequacy of representation, for example, a sample in which half of the total number are males and the other half are females. Greater Hagerstown is the metropolitan area in the state of Maryland. He led the Annapolis Convention, which successfully influenced Congress to issue a call for the Philadelphia Convention in order to create a new constitution, Hamilton became the leading cabinet member in the new government under President Washington.





The remainder are contributing resources within historic districts, each year approximately 30, properties are added to the National Register as part of districts or by individual listings. Population pyramid for Egypt, Calculation of the sex ratio score, and the age ratio scores for males and females: China smartphones online shopping New Hampshire, Rhode Island, and Connecticut soon raised similar, on July 18, the Congress requested all colonies form militia companies from all able bodied effective men, between sixteen and fifty years of age. Births and other vital events may be counted either by year of registration, the date when they were registered, or year of occurrence when the event actually took place. Portal site of official statistics of Japan.





Using procedure 1 outlined in Box 4. In my experience, this is particularly the case in the field of demography. Unexpectedly cold water can cause a swimmers muscles to weaken, it can also cause shock.









Hamilton was dispatched by Washington on numerous missions to convey plans to his generals, after the war, Hamilton was elected as a representative to the Congress of the Confederation from New York. Calculation of the index of concentration: They are the focus of this book. It is the county seat of Washington County, and the largest city in a known as Western Maryland. The result is congestion within the circle which could not clear without police intervention, the experience with traffic circles and rotaries in the USA was almost entirely negative, characterized by high accident rates and congestion problems. References 57 Table 3. The number of births in China during was estimated as

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25.03.2018 - Migration out of an area is known as emigration and that into an area is immigration. The coordinates are chosen such that one of the numbers represents a vertical position. Japan, using logarithmic scale to base Population pyramid for Senegal, The first chapter deals with the nature and historical context of demographic analysis. It also provided information on household size and composition, and type of housing tenure United Kingdom

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03.02.2018 - Preface ix Chapter 11 on projections ties together the concepts, methods, and data discussed in Chaps. In multiple regression one of the issues is the possibility that in addition to the relationship between the independent and the dependent variables, there is a also a relationship between two or more of the independent variables. The publisher makes no warranty, express or implied, with respect to the material contained herein. For example, if R is per 1, then R is divided by 1, before following procedures 1 or 2. Five years earlier, a band of unpaid soldiers besieged Congress while its members were meeting in Philadelphia, known as the Pennsylvania Mutiny ofthe event emphasized the need for the national government not to rely on any state for its own security. Washington captured a Hessian force at Trenton and drove the British out of New Jersey, in the British sent a new army under John Burgoyne to move south from Canada and to isolate the New England colonies. He ran all the lines by an instrument, and determined the acute angles by actual measurement.

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13.03.2018 - Inthe Treaty of Paris secured independence for each of the former colonies, with peace at hand, the states each turned toward their own internal affairs. A family is a household of two or more people who are related by union bonds, such as a couple, or some blood relationship such as a child-parent relationship. The last column has the percentage distribution of all persons according to income. Virginias economy changed from agricultural to industrial during the s and s. Hypothetical numeric data and calculation of moving averages. This model may take the following form: For instance, in a questionnaire, people are asked if they think that population growth is a major world problem and five possible response categories are given:

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Congressional districts are apportioned to states by using the United States Census results. Each state, regardless of population or size, has two senators, currently, there are senators representing the 50 states.

Each senator is elected at-large in their state for a term, with terms staggered. The House and Senate are equal partners in the legislative process—legislation cannot be enacted without the consent of both chambers, however, the Constitution grants each chamber some unique powers.

The Senate ratifies treaties and approves presidential appointments while the House initiates revenue-raising bills, the House initiates impeachment cases, while the Senate decides impeachment cases.

A two-thirds vote of the Senate is required before a person can be forcibly removed from office. The term Congress can also refer to a meeting of the legislature.

A Congress covers two years, the current one, the th Congress, began on January 3,, the Congress starts and ends on the third day of January of every odd-numbered year. Members of the Senate are referred to as senators, members of the House of Representatives are referred to as representatives, congressmen, or congresswomen.

One analyst argues that it is not a solely reactive institution but has played a role in shaping government policy and is extraordinarily sensitive to public pressure. Several academics described Congress, Congress reflects us in all our strengths, Congress is the governments most representative body.

Congress is essentially charged with reconciling our many points of view on the public policy issues of the day. Residence Act — The federal government was located in New York City at the time the bill was passed and had previously been located in Philadelphia, Annapolis, and several other locations.

Congress passed the Residence Act as part of a compromise brokered between James Madison, Thomas Jefferson, and Alexander Hamilton, Madison and Jefferson favored a southerly site for the capital on the Potomac River, but they lacked a majority to pass the measure through Congress.

Meanwhile, Hamilton was pushing for Congress to pass the Assumption Bill, with the compromise, Hamilton was able to muster support from the New York State delegates for the Potomac site, while four delegates switched from opposition to support for the Assumption Bill.

In the meantime, Philadelphia was chosen as a temporary capital, Washington had authority to appoint three commissioners and oversee the construction of Federal buildings in the District, something to which he gave much personal attention.

On account of British military actions, the Continental Congress was forced to relocate to Baltimore, Lancaster, Pennsylvania, Congress requested that John Dickinson, the governor of Pennsylvania, call up the militia to defend Congress from attacks by the protesters.

In what became known as the Pennsylvania Mutiny of, Dickinson sympathized with the protesters, as a result, Congress was forced to flee to Princeton, New Jersey on June 21,, and met in Annapolis and Trenton, before ending up in New York City.

The United States Congress was established upon ratification of the United States Constitution in, the question of where to establish the capital was raised in The Southern states refused to accept a capital in the North, another suggestion was for there to be two capitals, one in the North and one in the South.

Congress approved a plan in for a capital on the Potomac, near Georgetown, in Maryland, and another capital on the Delaware River, this plan was rescinded the following year.

Establishing the capital was put on hold for years, until the Constitutional Convention was held in The Constitution said nothing about where the district would be. The debate heated up in when Congress convened for the first time under the Constitution, two sites were favored by members of Congress, one site on the Potomac River near Georgetown, and another site on the Susquehanna River near Wrights Ferry.

The Susquehanna River site was approved by the House in September, while the Senate bill specified a site on the Delaware River near Germantown, Congress did not reach an agreement at the time.

The selection of a location for the capital resurfaced in the summer of, at the same time, Secretary of the Treasury Alexander Hamilton was pushing for Congress to pass a financial plan. A key provision of Hamiltons plan involved the Federal government assuming states debts incurred during the American Revolutionary War, northern states had accumulated a huge amount of debt during the war, amounting to The Southern states, whose citizens would effectively be forced to pay a portion of debt if the Federal Government assumed it.

As the first Secretary of the Treasury, Hamilton was the author of the economic policies of the George Washington administration. He took the lead in the funding of the debts by the Federal government, as well as the establishment of a national bank, a system of tariffs.

His vision included a central government led by a vigorous executive branch. This was challenged by Virginia agrarians Thomas Jefferson and James Madison who formed a rival party and they favored strong states based in rural America and protected by state militias as opposed to a strong national army and navy.

They denounced Hamilton as too friendly toward Britain and toward monarchy in general, Hamilton was born out of wedlock in Charlestown, to a married mother of British and French Huguenot ancestry and a Scottish father.

His father, James A. Hamilton, was the son of laird Alexander Hamilton of Grange. Orphaned as a child by his mothers death and his fathers abandonment, Hamilton was taken in by an older cousin and he was recognized for his intelligence and talent, and sponsored by a group of wealthy local men to travel to New York City to pursue his education.

Hamilton attended Kings College, choosing to stay in the Thirteen Colonies to seek his fortune, discontinuing his studies before graduating when the college closed its doors during British occupation of the city, Hamilton played a major role in the American Revolutionary War.

At the start of the war in, he joined a militia company, in early, he raised a provincial artillery company, to which he was appointed captain. He soon became the aide to General Washington, the American forces commander-in-chief.

Hamilton was dispatched by Washington on numerous missions to convey plans to his generals, after the war, Hamilton was elected as a representative to the Congress of the Confederation from New York.

He resigned to practice law, and founded the Bank of New York, Hamilton was among those dissatisfied with the weak national government. He led the Annapolis Convention, which successfully influenced Congress to issue a call for the Philadelphia Convention in order to create a new constitution, Hamilton became the leading cabinet member in the new government under President Washington.

These programs were funded primarily by a tariff on imports, to overcome localism, Hamilton mobilized a nationwide network of friends of the government, especially bankers and businessmen, which became the Federalist Party.

A major issue in the emergence of the American two-party system was the Jay Treaty and it established friendly trade relations with Britain, to the chagrin of France and the supporters of the French Revolution.

Hamilton played a role in the Federalist party, which dominated national. In, he returned to the practice of law in New York and he tried to control the policies of President Adams.

Thomas Jefferson — Thomas Jefferson was an American Founding Father who was the principal author of the Declaration of Independence and later served as the third President of the United States from to Previously, he was elected the second Vice President of the United States, Jefferson was primarily of English ancestry, born and educated in colonial Virginia.

Jefferson and James Madison organized the Democratic-Republican Party to oppose the Federalist Party during the formation of the First Party System, as President, Jefferson pursued the nations shipping and trade interests against Barbary pirates and aggressive British trade policies.

He also organized the Louisiana Purchase, almost doubling the countrys territory, as a result of peace negotiations with France, his administration reduced military forces.

Jeffersons second term was beset with difficulties at home, including the trial of former Vice President Aaron Burr, American foreign trade was diminished when Jefferson implemented the Embargo Act of, responding to British threats to U.

In, Jefferson began a process of Indian tribe removal to the newly organized Louisiana Territory. Jefferson mastered many disciplines, which ranged from surveying and mathematics to horticulture and he was a proven architect in the classical tradition.

Jeffersons keen interest in religion and philosophy earned him the presidency of the American Philosophical Society and he shunned organized religion, but was influenced by both Christianity and deism.

He was well versed in linguistics and spoke several languages and he founded the University of Virginia after retiring from public office. He was a letter writer and corresponded with many prominent and important people throughout his adult life.

His only full-length book is Notes on the State of Virginia, Jefferson owned several plantations which were worked by hundreds of slaves. Most historians now believe that, after the death of his wife in, he had a relationship with his slave Sally Hemings and fathered at least one of her children.

Various modern scholars are more critical of Jeffersons private life, pointing out the discrepancy between his ownership of slaves and his political principles, for example.

Presidential scholars, however, consistently rank Jefferson among the greatest presidents, Thomas Jefferson was born on April 13,, at the family home in Shadwell in the Colony of Virginia, the third of ten children.

He was of English and possibly Welsh descent and was born a British subject and his father Peter Jefferson was a planter and surveyor who died when Jefferson was fourteen, his mother was Jane Randolph.

Peter Jefferson moved his family to Tuckahoe Plantation in upon the death of a friend who had named him guardian of his children, the Jeffersons returned to Shadwell in, where Peter died in, his estate was divided between his sons Thomas and Randolph.

Thomas inherited approximately 5, acres of land, including Monticello and he assumed full authority over his property at age The river is approximately miles long, with an area of about 14, square miles.

In terms of area, this makes the Potomac River the fourth largest river along the Atlantic coast of the United States, over 5 million people live within the Potomac watershed. The river forms part of the borders between Maryland and Washington, D.

The majority of the lower Potomac River is part of the State of Maryland, exceptions include a small tidal portion within the District of Columbia, and the border with Virginia being delineated from point to point.

Except for a portion of its headwaters in West Virginia. The largest flow recorded on the Potomac at Washington, D. The estuary also widens, reaching 11 statute miles wide at its mouth, Potomac is a European spelling of Patowmeck, the Algonquian name of a Native American village, perhaps meaning something brought.

Native Americans had different names for different parts of the river, calling the river above Great Falls Cohongarooton, meaning honking geese and Patawomke below the fall, meaning river of swans.

The spelling of the name has many forms over the years from Patawomeke to Patawomeck, Patowmack. The rivers name was decided upon as Potomac by the Board on Geographic Names in The river itself is at least two years old, likely extending back ten to twenty million years before present when the Atlantic Ocean lowered and exposed coastal sediments along the fall line.

The name Anacostia derives from the early history as Nacotchtank. Heavy pollution in the Anacostia and weak investment and development along its banks have led to it becoming what many have called D.

Maryland and federal governments have made joint efforts to reduce its pollution levels in order to protect the ecologically valuable Anacostia watershed, the mainstem of the Anacostia is formed by the confluence of the Northwest Branch and the Northeast Branch just north of Bladensburg, Maryland.

The watershed of the river roughly covers sq mi in eastern Montgomery County and northern Prince Georges County, as well as parts of Washington, on earlier maps, the river was known as the Eastern Branch of the Potomac River until it received its current, official name.

The Washington City Canal operated from until the mids, initially connecting the Anacostia to Tiber Creek and the Potomac River, the city canal fell into disuse in the late 19th century, and the city government covered over or filled in various sections.

One of the biggest problems facing the Anacostia River is raw sewage that enters the river, the sewage creates a public health threat because of fecal coliform bacteria and other pathogens, it also impairs water quality and can create hypoxic conditions that lead to large fish kills.

C, water and Sewer Authority in for allowing more than 2,,, US gallons of combined sewage and urban runoff to flow into the river via its antiquated combined sewer overflow system.

In late, AWS and other organizations announced plans to sue the Washington Suburban Sanitary Commission over similar problems with contamination from the Maryland suburbs.

Another large source of pollution is the Washington Navy Yard. In its first year of operation, it removed more than pounds of litter per month from the river. Conococheague Creek — Conococheague Creek, a tributary of the Potomac River, is a free-flowing stream that originates in Pennsylvania and empties into the Potomac River near Williamsport, Maryland.

It is 80 miles in length, with 57 miles in Pennsylvania and 23 miles in Maryland, the watershed of Conococheague Creek has an area of approximately square miles, out of which only 65 square miles are in Maryland.

The creek flows southwest, turning west at Caledonia State Park, the creek from Fayetteville to its confluence with Back Creek near Williamson is very polluted from farm runoff.

This in turn has made parts of the lower East Branch ideal for catching huge crayfish at night, however, the West Branch flows for The West Branch is the pure of the two, owing mostly to the fact that a large portion of it runs through wilderness, making for very fine smallmouth bass, warmouth.

However, there are a few small sewage treatment plants on the lower West Branch, starting at Fort Loudon, northern pike and pickerel have been caught in the creek. It was listed on the National Register of Historic Places in, the crossing is where Braddocks forces crossed the Potomac after leaving Frederick on their way to Winchester.

It is the county seat of Washington County, and the largest city in a known as Western Maryland. The population of Hagerstown city proper at the census was 39,, Hagerstown ranks as Marylands sixth largest incorporated city.

Hagerstown has a distinct topography, formed by stone ridges running from northeast to southwest through the center of town and these ridges consist of upper Stonehenge limestone. Many of the buildings were built from this stone, which is easily quarried and dressed onsite.

It whitens in weathering and the conglomerate and wavy laminae become distinctly visible, giving a handsome. Brick and concrete eventually displaced this native stone in the construction process, the population of the metropolitan area in was, Greater Hagerstown is the metropolitan area in the state of Maryland.

Despite its semi-rural Western Maryland setting, Hagerstown is a center of transit, interstates 81 and 70, CSX, Norfolk Southern, and the Winchester and Western railroads, and Hagerstown Regional Airport form an extensive transportation network for the city.

Hagerstown has often referred to as, and is nicknamed. A person born in Hagerstown is officially called a Hagerstonian, in, Hager officially founded the town of Elizabethtown which he named after his wife, Elizabeth Kershner.

In government forces arrested citizens during a riot which was staged by protesters in response to the Whiskey Rebellion. Hagerstowns strategic location at the border between the North and the South made the city a primary staging area and supply center for four major campaigns during the Civil War, in, General Robert Pattersons troops used Hagerstown as a base to attack Virginia troops in the Shenandoah Valley.

In, the city was the site of military incursions. In, Hagerstown was invaded by the Confederate army under Lt. John McCausland, into Hagerstown. The spread of smallpox by returning soldiers to families and friends was a problem during the war.

Founded in in the Province of Maryland, the port of Georgetown predated the establishment of the federal district, Georgetown remained a separate municipality until, when the United States Congress created a new consolidated government for the whole District of Columbia.

A separate act passed in specifically repealed Georgetowns remaining local ordinances, Georgetown is home to the main campus of Georgetown University and numerous other landmarks, such as the Volta Bureau and the Old Stone House, the oldest unchanged building in Washington.

The embassies of Cameroon, France, Kosovo, Iceland, Liechtenstein, Mongolia, Sweden, Thailand, Ukraine, situated on the fall line, Georgetown was the farthest point upstream that oceangoing boats could navigate the Potomac River.

In, English fur trader Henry Fleet documented a Native American village of the Nacotchtank people called Tohoga on the site of present-day Georgetown, the area was then part of the Province of Maryland, an English colony.

George Gordon constructed a tobacco inspection house along the Potomac in approximately, the site was already a tobacco trading post when the inspection house was built. Warehouses, wharves, and other buildings were constructed around the inspection house.

It did not take long before Georgetown grew into a port, facilitating trade. In, the legislature of the Province of Maryland authorized the purchase of 60 acres of land from Gordon, a survey of the town was completed in February The Maryland Legislature formally issued a charter and incorporated the town in, robert Peter, an early area merchant in the tobacco trade, became Georgetowns first mayor in In, the Trinity Catholic Church was built, along with a parish school-house, construction of St.

Johns Episcopal Church began in, but paused for financial reasons until, and the church was finally consecrated in Fulton began publishing the Potomac Advocate, which was started by Thomas Turner.

Other newspapers in Georgetown included the Georgetown Courier and the Federal Republican, magruder, the first postmaster, was appointed on February 16,, and in, a custom house was established on Water Street.

Lingan served as the first collector of the port, in the s, City Tavern, the Union Tavern, and the Columbian Inn opened and were popular throughout the 19th century. Of these taverns, only the City Tavern remains today, as a social club located near the corner of Wisconsin Avenue.

As of the census, the population was, and it is the most populous county in Maryland. The county seat and largest municipality is Rockville, although the place of Germantown is the most populous place.

In, it was ranked by Forbes as the 10th richest in the United States, the Maryland state legislature named Montgomery County after Richard Montgomery, the county was created from lands that had at one point or another been part of Frederick County.

The countys motto, adopted in, is Gardez Bien, the countys motto is also the motto of its namesakes family. Before European immigration, the now known as Montgomery County was covered in a vast swath of forest crossed by the creeks and small streams that feed the Potomac.

A few small villages of the Piscataway, members of the Algonquian people, were scattered across the southern portions of the county. Captain John Smith of the English settlement at Jamestown was probably the first European to explore the area, during his travels along the Potomac River and throughout the Chesapeake region.

These lands were claimed by Europeans for the first time when George Calvert and he and other early claimants had no intention of settling their families. They were little more than speculators, securing grants from the colonial leadership, thus, it was not until approximately that the first British settlers began building farms and plantations in the area.

Most of these settlers were small farmers, growing wheat. Many of the farmers owned slaves and they transported the tobacco they grew to market through the Potomac River port of Georgetown.

Sparsely settled, the farms and taverns were nonetheless of strategic importance as access to the interior. General Edward Braddocks army traveled through the county on the way to its disastrous defeat at Fort Duquesne during the French, like other regions of the American colonies, the region that is now Montgomery County saw protests against British taxation in the years before the American Revolution.

In, local residents met at Hungerfords Tavern and agreed to break off commerce with Great Britain, following the signing of the Declaration of Independence, representatives of the area helped to draft the new state constitution and began to build a Maryland free of proprietary control.

The leaders of the new county chose as their county seat an area adjacent to Hungerfords Tavern near the center of the county, the newly formed Montgomery County supplied arms, food and forage for the Continental Army during the Revolution, in addition to soldiers.

Maryland — The states largest city is Baltimore, and its capital is Annapolis. George Calvert was the first Lord of Baltimore and the first English proprietor of the colonial grant.

Maryland was the state to ratify the United States Constitution. Maryland is one of the smallest U. It is the 42nd largest and 9th smallest state and is closest in size to the state of Hawaii, the next largest state, its neighbor West Virginia, is almost twice the size of Maryland.

Maryland possesses a variety of topography within its borders, contributing to its nickname America in Miniature. The mid-portion of this border is interrupted by Washington, D.

This land was ceded to the United States Federal Government in to form the District of Columbia, the Chesapeake Bay nearly bisects the state and the counties east of the bay are known collectively as the Eastern Shore.

Close to the town of Hancock, in western Maryland, about two-thirds of the way across the state. This geographical curiosity makes Maryland the narrowest state, bordered by the Mason—Dixon line to the north, portions of Maryland are included in various official and unofficial geographic regions.

The lack of any glacial history accounts for the scarcity of Marylands natural lakes, laurel Oxbow Lake is an over one-hundred-year-old acre natural lake two miles north of Maryland City and adjacent to Russett.

Chews Lake is a natural lake two miles south-southeast of Upper Marlboro. There are numerous lakes, the largest of them being the Deep Creek Lake. Maryland has shale formations containing natural gas, where fracking is theoretically possible, as is typical of states on the East Coast, Marylands plant life is abundant and healthy.

Middle Atlantic coastal forests, typical of the southeastern Atlantic coastal plain, grow around Chesapeake Bay, moving west, a mixture of Northeastern coastal forests and Southeastern mixed forests cover the central part of the state.

It is coterminous with the U. Census Bureau-census-designated place of Arlington, as a result, the county is often referred to in the region simply as Arlington or Arlington, Virginia.

In, the population was estimated at, The land that became Arlington was originally donated by Virginia to the United States government to form part of the new federal district of Columbia.

In, Congress returned the land southwest of the Potomac River donated by Virginia due to issues involving Congressional representation, the General Assembly of Virginia changed the countys name to Arlington in to avoid confusion with the adjacent City of Alexandria.

The county is situated in Northern Virginia on the bank of the Potomac River directly across from Washington. Arlington is also bordered by Fairfax County and City of Falls Church to the northwest, west and southwest, as of the census, the population was, Due to the proximity to downtown Washington, D.

It is also home to Ronald Reagan Washington National Airport, the many federal agencies, government contractors, and service industries contribute to Arlingtons stable economy.

It is the county in the United States by median family income. According to a study by Bankrate. Land grants from the British monarch were awarded to prominent Englishmen in exchange for political favors, one of the grantees was Thomas Fairfax, 6th Lord Fairfax of Cameron, who lends his name to both Fairfax County and the City of Fairfax.

With the passage of the Residence Act in, Congress approved a new permanent capital to be located on the Potomac River, the Residence Act originally only allowed the President to select a location within Maryland as far east as what is now the Anacostia River.

However, President Washington shifted the federal territorys borders to the southeast in order to include the city of Alexandria at the Districts southern tip.

In, Congress amended the Residence Act to approve the new site, however, this amendment to the Residence Act specifically prohibited the erection of the public buildings otherwise than on the Maryland side of the River Potomac.

As permitted by the U. Constitution, the shape of the federal district was a square, measuring 10 miles on each side. As of the census, the population was 1,,, in, it was estimated at 1,,, making it the Commonwealths most populous jurisdiction, with The county seat is the City of Fairfax, though because it is an independent city under Virginia law, the county is also home to seven Fortune companies, including three with Falls Church addresses.

At the time of European encounter, the inhabitants of what would become Fairfax County were an Algonquian-speaking sub-group called the Taux, also known as the Doeg or Dogue.

Their villages, as recorded by Captain John Smith in, included Namassingakent, virginian colonists from the Northern Neck region drove the Doeg out of this area and into Maryland by Fairfax County was formed in from the part of Prince William County.

Thomas Fairfax, 6th Lord Fairfax of Cameron, the member of the British nobility ever to reside in the colonies. The Belvoir mansion and several of its outbuildings were destroyed by fire immediately after the Revolutionary War in, in, the northwestern two-thirds of Fairfax County became Loudoun County.

Alexandria County was returned to Virginia in, reduced in size by the secession of the independent city of Alexandria in, the Fairfax County town of Falls Church became an independent city in The federal governments growth during and after World War II spurred rapid growth in the county, other large businesses continued to settle in Fairfax County and the opening of Tysons Corner Center spurred the rise of Tysons Corner.

The technology boom and a steady government-driven economy also created rapid growth, the economy has also made Fairfax County one of the nations wealthiest counties.

Virginia — Virginia is a state located in the Mid-Atlantic region of the United States, as well as in the historic Southeast. The geography and climate of the Commonwealth are shaped by the Blue Ridge Mountains and the Chesapeake Bay, the capital of the Commonwealth is Richmond, Virginia Beach is the most populous city, and Fairfax County is the most populous political subdivision.

The Commonwealths estimated population as of is over 8. In the London Company established the Colony of Virginia as the first permanent New World English colony, slave labor and the land acquired from displaced Native American tribes each played a significant role in the colonys early politics and plantation economy.

Although the Commonwealth was under one-party rule for nearly a century following Reconstruction, the Virginia General Assembly is the oldest continuous law-making body in the New World. The state government was ranked most effective by the Pew Center on the States in both and and it is unique in how it treats cities and counties equally, manages local roads, and prohibits its governors from serving consecutive terms.

Virginias economy changed from agricultural to industrial during the s and s. Virginia has an area of 42, Virginias boundary with Maryland and Washington, D. The Chesapeake Bay separates the portion of the Commonwealth from the two-county peninsula of Virginias Eastern Shore.

The bay was formed from the river valleys of the Susquehanna River. Many of Virginias rivers flow into the Chesapeake Bay, including the Potomac, Rappahannock, York, and James, the Tidewater is a coastal plain between the Atlantic coast and the fall line.

It includes the Eastern Shore and major estuaries of Chesapeake Bay, the Piedmont is a series of sedimentary and igneous rock-based foothills east of the mountains which were formed in the Mesozoic era.

The region, known for its clay soil, includes the Southwest Mountains around Charlottesville. The Blue Ridge Mountains are a province of the Appalachian Mountains with the highest points in the state.

The Ridge and Valley region is west of the mountains and includes the Great Appalachian Valley, the region is carbonate rock based and includes Massanutten Mountain. The Cumberland Plateau and the Cumberland Mountains are in the southwest corner of Virginia, in this region, rivers flow northwest, with a dendritic drainage system, into the Ohio River basin.

Since its foundation in its present form in, it has been part of the National Oceanic and Atmospheric Administration, the National Geodetic Surveys history and heritage are intertwined with those of other NOAA offices.

Coast Survey and U. S, upon the creation of the Environmental Science Services Administration in, the commissioned corps was separated from the Survey to become the Environmental Science Services Administration Corps.

The NSRS may be divided into its geometric and physical components, the official geodetic datum of the United States, NAD83 defines the geometric relationship between points within the United States in three-dimensional space.

This datum is a network of orthometric heights obtained through spirit leveling, NGS will release new datums in United States territories on the Pacific, Caribbean, and Mariana plates will have their own respective geodetic datums, the North American-Pacific Geopotential Datum of will separately define the height system of the United States and its territories, replacing NAVD It will use a geoid model accurate to 1 centimeter to relate orthometric height to ellipsoidal height measured by GPS, NGS provides a number of other public services.

A Swiss immigrant with expertise in surveying and the standardization of weights and measures, Ferdinand R. Hassler, was selected to lead the Survey. Hassler departed on August 29,, but eight months later, while he was in England, Hassler did not return to the United States until August 16, The Survey finally began surveying operations in, when Hassler started work in the vicinity of New York City, the first baseline was measured and verified in Navy responsibility for coastal surveys, Hassler was reappointed as the Surveys superintendent that year.

Quarry — A quarry is a place from which dimension stone, rock, construction aggregate, riprap, sand, gravel, or slate has been excavated from the ground.

A quarry is the thing as an open-pit mine from which minerals are extracted. The only non-trivial difference between the two is that open-pit mines that produce building materials and dimension stone are commonly referred to as quarries, the word quarry can also include the underground quarrying for stone, such as Bath stone.

The surfaces are polished and finished with varying degrees of sheen or luster, polished slabs are often cut into tiles or countertops and installed in many kinds of residential and commercial properties.

Natural stone quarried from the earth is considered a luxury and tends to be a highly durable surface. Quarries in level areas with shallow groundwater or which are located close to surface water often have engineering problems with drainage, generally the water is removed by pumping while the quarry is operational, but for high inflows more complex approaches may be required.

For example, the Coquina quarry is excavated to more than 60 feet below sea level, to reduce surface leakage, a moat lined with clay was constructed around the entire quarry. Ground water entering the pit is pumped up into the moat, as a quarry becomes deeper, water inflows generally increase and it also becomes more expensive to lift the water higher during removal, this can become the limiting factor in quarry depth.

Some water-filled quarries are worked from beneath the water, by dredging, many people and municipalities consider quarries to be eyesores and require various abatement methods to address problems with noise, dust, and appearance.

One of the effective and famous examples of successful quarry restoration is Butchart Gardens in Victoria, BC. A further problem is pollution of roads from trucks leaving the quarries, to control and restrain the pollution of public roads, wheel washing systems are becoming more common.

Many quarries naturally fill with water after abandonment and become lakes, water-filled quarries can be very deep with water, often 50 feet or more, that is often surprisingly cold.

Unexpectedly cold water can cause a swimmers muscles to weaken, it can also cause shock. Though quarry water is very clear, submerged quarry stones. Several people drown in quarries each year, however, many inactive quarries are converted into safe swimming sites.

Public Quarry at Government Island — Washington selected Aquia sandstone as the primary material for use in Washingtons government buildings. Acting on the governments behalf, the Wiggintons Island quarry was purchased by Pierre Charles LEnfant in, use of the stone declined as its susceptibility to weathering was observed, and the quarry became worked out and derelict after the U.

The property was sold by the U. Government in, the property was acquired by Stafford County as a county park and opened to the public on November 6, with trails and markers highlighting the historical significance of the island.

It was listed on the National Register of Historic Places in Aquia Creek — Aquia Creek is a The creeks headwaters lie in southeastern Fauquier County, and it empties into the Potomac at Brent Point in Stafford County,45 miles south of Washington, the Public Quarry at Government Island in the creek served as the source for Aquia Creek sandstone.

This sandstone was used in public buildings, the National Capitol Columns were quarried in the early s. Aquia Creek sandstone — Aquia Creek sandstone is a type of brown to light-gray freestone used extensively in building construction in Washington, D.

The sandstone was the material used in such significant buildings as the White House. The easy availability of the stone and its ability to be carved were offset in time by its susceptibility to weather-induced deterioration and its best, most enduring uses were as interior decorative elements.

Of Cretaceous age, Aquia Creek sandstone is composed of rounded, coarse - to fine-grains of quartz, cemented with silica and this sandstone is typically gray or tan, sometimes with streaks or shades of red, yellow or buff, giving the stone a warm effect.

Washington selected Aquia sandstone as the material for use in Washingtons government buildings. Acting on the governments behalf, the Wiggintons Island quarry was purchased by Pierre Charles LEnfant in, the stone from the quarry was used by James Hoban for the Presidents House and the Capitol.

The earliest portions of the Treasury Building and the Patent Office also used the stone, both the Capitol and the Presidents House were burned during the War of, cracking and pitting the sandstone, and requiring extensive repair.

Both buildings were whitewashed and later painted to hide damage and protect the stone from weathering, one of the last major uses of the material was at the U. Capitol gatehouses and gateposts, designed by Charles Bulfinch about A good example of Aquia Creek sandstone as it was used in architecture is the relocated National Capitol Columns now at the National Arboretum.

The best places to see Aquia Creek sandstone as it was used indoors are in the parts of the U. The sandstone gallery of the building, with its plain squat columns, is particularly impressive.

In the Capitol Building, the stone may be seen in the walls and columns of the adjoining the rotunda. The graceful Little Rotunda tobacco column colonnade in the Senate wing on this floor, downstairs, the simple Doric columns of the crypt have a brownish cast, while the famous cornstalk columns in a nearby entrance hall are decidedly gray.

Capitol Gatehouses and Gateposts U. Foundation engineering — A foundation is the element of an architectural structure which connects it to the ground, and transfers loads from the structure to the ground.

Foundations are generally considered either shallow or deep, foundation engineering is the application of soil mechanics and rock mechanics in the design of foundation elements of structures.

Buildings and structures have a history of being built with wood in contact with the ground. Post in ground construction may technically have no foundation, timber pilings were used on soft or wet ground even below stone or masonry walls.

In marine construction and bridge building a crisscross of timbers or steel beams in concrete is called grillage, perhaps the simplest foundation is the padstone, a single stone which both spreads the weight on the ground and raises the timber off the ground.

Staddle stones are a type of padstone. Dry stone and stones laid in mortar to build foundations are common in parts of the world. Dry laid stone foundations may have painted with mortar after construction.

Sometimes the top, visible course of stone is hewn, quarried stones, besides using mortar, stones can also be put in a gabion. One disadvantage is that if using regular steel rebars, the gabion would last much less long than when using mortar, using weathering steel rebars could reduce this disadvantage somewhat.

Rubble trench foundations are a shallow trench filled with rubble or stones and these foundations extend below the frost line and may have a drain pipe which helps groundwater drain away.

One common type is the spread footing which consists of strips or pads of concrete which extend below the frost line and transfer the weight from walls and columns to the soil or bedrock.

Another common type of foundation is the slab-on-grade foundation where the weight of the building is transferred to the soil through a concrete slab placed at the surface. A deep foundation is used to transfer the load of a structure down through the upper layer of topsoil to the stronger layer of subsoil below.

There are different types of deep footings including impact driven piles, drilled shafts, caissons, helical piles, geo-piers, the naming conventions for different types of footings vary between different engineers.

Historically, piles were wood, later steel, reinforced concrete, a large number of monopile foundations have been utilized in recent years for economically constructing fixed-bottom offshore wind farms in shallow-water subsea locations.

For example, a wind farm off the coast of England went online in with over turbines. Andrew Ellicott — Andrew Ellicott was a U. Andrew Ellicott was born in Buckingham Township, Bucks County, Pennsylvania as the first of nine children of Joseph Ellicott, the Quaker family lived in modest conditions, his father was a miller and clockmaker.

Young Andrew was educated at the local Quaker school, where Robert Patterson, Andrew was a talented mechanic like many of the family and showed some mathematical talent, too. In, his father, together with his uncles Andrew and John, purchased land on the Patapsco River and set up a new milling business there, founding the town of Ellicotts Mills in Three years later, Andrew married Sarah Brown of Newtown, Pennsylvania, with whom he would have ten children, when the Revolutionary War broke out, Andrew enlisted as a commissioned officer in the Elk Ridge Battalion of the Maryland militia despite his Quaker upbringing.

During the course of the war, he rose to the rank of major, in this survey, he worked alongside David Rittenhouse and James Madison, making first connections with the scientific society of Philadelphia.

Following the death of their son, the Ellicotts moved to Baltimore in The same year, he was called upon for a survey to define the border of Pennsylvania.

This Ellicott Line later became the meridian for the surveys of the Northwest Territory. His work in Pennsylvania intensified his ties with Rittenhouse and other members of the American Philosophical Society and led to encounters with Benjamin Franklin, when he was subsequently appointed to lead other surveys in Pennsylvania, the family moved again in to Philadelphia.

Territory, resulting in the Erie Triangle and this survey, during which he also made the first topographical study of the Niagara River including the Niagara Falls, gained Ellicott a reputation for superb accuracy in surveys.

He was assisted in this survey first by the free African-American astronomer Benjamin Banneker and then by Ellicotts brothers, Joseph Ellicott, Ellicotts team put into place forty boundary stones approximately 1 mile apart from each other that marked the borders of the Territory of Columbia of square miles.

Most of these remain in their original positions. As engravings on many of the stones still show, Ellicotts team placed those that marked the border with Virginia in, and those that marked the border with Maryland in During —, Ellicott also surveyed the city of Washington.

Ellicott also served under the Commissioners supervision in this effort, however, LEnfant subsequently entered into a number of conflicts with the Commissioners and others involved in the enterprise.

Ellicott, with the aid of his brother, Benjamin Ellicott, then revised the plan, Ellicott gave the first version of his own plan to James Thakara and John Valance of Philadelphia, who engraved, printed and published it.

This version, printed in March, was the first Washington city plan that received wide circulation, after LEnfant departed, Ellicott continued the city survey in accordance with his revised plan, several larger and more detailed versions of which were also engraved, published and distributed.

During November—December, he led a survey that helped settle a dispute within the present Ontario County in western New York state. From, he was employed as a surveyor and draftsman for the Holland Land Company, in, he was in charge of the companys surveys in western New York.

Ellicott was elected as a Democratic-Republican representative from New York to the Fifteenth Congress and he was an unsuccessful candidate for election in to the Seventeenth Congress.

He then retired from life and in moved to Williamsville, New York. He was interred in the graveyard at Williamsville and he was reinterred in Batavia Cemetery, Batavia, New York, in Randolph Square — The Randolph Square Matter was used as a euphemism for the dust up which eventually led George Washington to fire LEnfant, and turn the design project over to Ellicott.

After the Revolutionary War, George Washington involved himself personally in the building of a capital on the Potomac River. In, Washington appointed LEnfant to design the layout of the new capital city, also heavily involved in the planning of the capital city was Thomas Jefferson, whose image for the future capital was egalitarian and simple, even understated.

Over the course of, LEnfant created his plan for the city, full of symbolic design elements and sweeping vistas. But as LEnfant began to run into road blocks related to cost and just how grand he intended the new city to become, Washington attempted to intervene on LEnfants behalf, but eventually the tide had turned too far against the French architect.

LEnfant was effectively removed from the project and would spend the rest of his living off of friends. LEnfants plan for the city included a grid plan, overlaid with diagonal avenues radiating from the Presidents House.

Due to the large intersections created when diagonal streets met grid intersections, LEnfant installed a number of squares, among these squares was a square bordered by 7th and 9th streets NW and by S and R streets NW.

The Square, labeled Square No. There are various theories as to why the changes were made to the city in Ellicotts new map, in her book, Washington in Maps, Iris Miller suggests it may have been due in no small part to Ellicotts lack of vision.

Examine Elements from LEnfants plan that Ellicott declined to grasp, one finds that Ellicotts engravings reflect the hand and mentality of an American-trained surveyor - not a European urban artist.

These responded to variations in topography that influenced spatial perception, Ellicotts regularized application of this plan neglected to account for design illusions that enhance urbanism.

It cannot be ignored, however, that LEnfant was extremely unpopular by the time Ellicott took over the project and he was known as the crazy Frenchman, blew through his budget, made demands on officials and landowners alike, and made life generally unpleasant for many around him.

Ellicott had been working with LEnfant throughout the project and was a personal confidant of Jefferson who had become a strong critic of the architect.

Washington mourned the removal of his friend from the position of architect of the Capital city, today, the area which would have been Randolph Square is located in the Shaw Neighborhood in Washington.

Situated to the west of the palace, the gardens cover some hectares of land, in addition to the meticulous manicured lawns, parterres of flowers, and sculptures are the fountains, which are located throughout the garden.

On weekends from spring to early autumn, the administration of the museum sponsors the Grandes Eaux — spectacles during which all the fountains in the gardens are in full play.

Records indicate that late in the decade Claude Mollet and Hilaire Masson designed the gardens and this early layout, which has survived in the so-called Du Bus plan of c.

This is evidenced in the definition of the main east-west. At every stage the prescribed tour was managed, under the Sun Kings directions. It provided an area in which orange trees were kept during the winter months.

With this new phase of construction, the gardens assumed the topographical and iconological design vocabulary that would remain in force until the 18th century. Escarpment — An escarpment is a steep slope or long cliff that forms as an effect of faulting or erosion and separates two relatively level areas of differing elevations.

Usually escarpment is used interchangeably with scarp, but some sources differentiate the two terms, where escarpment refers to the margin between two landforms, while scarp is synonymous with a cliff or steep slope.

The surface of the slope is called a scarp face. Sample surveys concerned with employment are carried out in most countries. Their frequency allows the study of trends over time and seasonality.

Their usefulness is often enhanced by piggybacking questions concerned with other subjects as in the case of the Australian Multi-Purpose Household Survey Australia Housing and household sample surveys can be particularly useful in countries that take a regular census.

For instance, the English Housing Survey —10 collected information on age, economic status, ethnicity and marital status and income of the household reference person.

It also provided information on household size and composition, and type of housing tenure United Kingdom Household sample surveys are conducted frequently to assess household income and expenditure 2.

Yet, other sample surveys collect data on a range of human activities including how people use their time Australia They were followed by the Demographic and Health Surveys, again among many developing countries to gain information on fertility, mortality and health related issues Zuehike Other countries also conduct surveys with a focus on health status.

However, its degree of completion varies depending on the level of civil administration of a country and difficulties in reaching people in less accessible areas. Accordingly, some countries have to rely on sample surveys and other methods to gain a more complete view of fertility and mortality, especially in rural areas.

In some countries, registration data can be more a source of confusion than usefulness, as far as demographic information is concerned, and care needs to be taken in testing its coverage and reliability; while in others these data are most valuable.

Birth registration can present problems such as the distinction between live and stillbirths and related measures of birth and perinatal death rates Sect. This can lead to both the under-enumeration of live births and infant mortality.

Death registration generally records the age and sex of the individual, place of birth, marital status, occupation and cause of death. Records can suffer from various shortcomings.

The first is the question of completeness of coverage due to similar issues as those of birth registration. Further, details regarding age, marital status and occupation can also pose challenges due to definitions and memory lapses.

The cause of death is also an issue in terms of definitions. There can also be lack of coverage because, in some cases, deaths may take place without medical assessment of the cause of death.

The value of registration data on marriages and divorces, as a source of information on family relationships is changing considerably, as social values and partnerships evolve.

Registration usually records de jure but not de facto relationships or separations. De facto marital status has risen considerably in some countries. This 16 2 Demographic Information has led to some countries to offer legal status to cohabitation and even registration without legal marriage OECD Further, there may be differences in legal statutes concerning marriage and divorce within the same country and across countries.

Nevertheless, marriage registration continues to provide information on a dimension of social relationships: The recorded information usually includes the date of the event and of birth and sex of the partners, their usual residence, occupation and religion, as well as any previous legal marital status.

In addition, divorce may also include the information on any children involved. However, they can be useful sources of demographic data United Nations They provide for the systematic record of the identity and characteristics of each individual resident either in a country or an area within.

The data recorded may include the date of birth, sex, marital status, place of birth and nationality. In some cases, a unique number may be given to each individual on the register.

For a population register to supply reliable statistics it should have attributes such as: The accuracy and timeliness of the data in population registers can be affected when vital events and statistics are recorded by different agencies and the register is dependent on record linkage from more than one source.

In some instances, delay in the transmission of information from local area registers to central agencies can affect their accuracy Netherlands Yet, another issue is international and internal migration that may lead to duplication or omission due to differences in definitions to distinguish visitors from residents.

Concerns have also been raised about the confidentiality of a wide range of information about a single individual in a given source. Some approaches to data handling can reduce some of the risks involved.

Similar issues have been raised about confidentiality of census information. Some Scandinavian and other countries are compiling their censuses from their population registers and complement them with other sources.

For instance, Finland has established a Population Register Centre and uses an individual identity number. The Central Population Register began to function in In, the 2. Population registers can also be used to estimate both international and internal migration.

This primary function may pose problems in the collection of demographic data because of: However, they also found that some people registered in these programs had been missed by the census.

This implies that although administrative records may be, at times, of poor quality they may also contain useful information. An advantage in the use of administrative records is that most of the large costs involved in data collection have already been incurred.

The growing use of electronic data entry and classification has also improved retrieval of these data and their manipulation for statistical purposes. Greater demand for statistics, concern with data collection fatigue and sometimes budgetary constraints have contributed to efforts in the use of administrative records as a source of statistics Brackstone Administrative records collect a wide range of information at various levels from countrywide programs such as taxation and social security benefits to local government administrative concerns such as housing.

The registration of vital events has already been discussed as a source of demographic information Sect. Statistics from schools are a major source of information on enrolments and levels of education achieved.

Hospital statistics can contribute to the assessment of dimensions of health status. Administrative records of international arrivals and departures and the granting of visas are useful in the estimation of international migration.

Taxation statistics can also be used to assess levels of income and also about the movement of people from year to year. The same applies to data kept by public utilities such as electricity, gas and water services.

They may collect the data from primary sources through censuses and surveys or retrieve data from other agencies, individuals or corporations. Information may be made available in a variety of media and through several means.

These include publications, special tabulations, samples of individual records in electronic media or through the Internet. All of these publications provide demographic information on a periodic basis.

The World Bank produces a World Development Report and various regional agencies also compile and publish a range of demographic information. In addition to publications, most national and international agencies also provide demographic data on their websites through the Internet.

Links to some of the major organisations are given below: Concepts, sources and methods, Apr Australian Bureau of Statistics. How Australians use their time, Perinatal deaths, Australia Household and family projections, Australia, to Census dictionary Australia Issues in the use of administrative records for statistical purposes.

Survey Methodology, 13 1 , 29— The world fertility survey: An assessment of its contribution. Internet, mail, and mixed-mode surveys: The tailored design method. Life table estimates for the Philippines, its regions and provinces, by sex: Use of registers and administrative data for statistical purposes: Best practices of Statistics Finland.

Annual report on the family income and expenditure survey Statistics on the causes of death, Malaysia Cohabitation rate and prevalence of other forms of partnership. Organization for Economic Cooperation and Development.

The World Fertility Survey: An international program of fertility research. Studies in Family Planning, 5 2 , 35— A manual for sociology students. Department for Communities and Local Government. Principles and recommendations for population and housing censuses — revision 2 Statistical papers series M no.

National health interview survey. Centers for Disease Control and Prevention. International classification of diseases ICD. The demographic and health surveys at 25 years and beyond. Chapter 3 Some Basic Statistical Measures 3.

The concepts are defined in general terms without going into theoretical details. Methods of calculation of various measures are described. The statistical measures discussed in this chapter consist of counts, frequencies, proportions, rates, various measures of central tendency, dispersion, comparison, correlation and regression.

This is useful because the level of measurement helps the selection of what statistical analysis is most appropriate. Several classifications can be used. This book uses the four-fold classification system proposed by Stevens that classifies data as being 1 nominal, 2 ordinal, 3 interval and 4 ratio.

There are other systems such as the two-fold classification of 1 discrete and 2 continuous. In the classification system proposed by Stevens, the nominal level is known as the lowest level of measurement.

Here, the values just name the attribute uniquely and do not imply an ordering of cases. For example, the variable marital is inherently nominal. In a study it might be useful to have attributes such as never married, married, separated, divorced and widowed.

These attributes are mutually exclusive and exhaustive. In the latter, the numbers are not numbers in a real sense since they cannot be added or subtracted.

Thus, numbers assigned to serve as values for nominal level variables such as marital status cannot be added, subtracted, multiplied or divided in a meaningful way. An exception is the dummy coding of F.

Dummy coding allows some limited functions to be performed. The next level of measurement is ordinal. Although it is at a higher level of measurement than the nominal category, it is still considered a low level of measurement.

The attributes are rank-ordered but the distances between the attributes are not fixed. For instance, in a questionnaire, people are asked if they think that population growth is a major world problem and five possible response categories are given: It can be seen that strongly agree coded as 5 indicates more agreement than a response coded as 4 somewhat agree, and so on.

However, the distance between the five categories is not fixed. It cannot be said whether the distance from strongly disagree 1 to somewhat disagree 2 is the same as that from strongly agree 5 to somewhat agree 4.

All it can be said is that codes 1 to 5 preserve the order of agreement. Coding ordinal levels with numbers is a grey area between the coding with numbers at nominal level for which there is no meaningful addition, subtraction, multiplication and division and interval level numbers that can be added and subtracted, and ratio level numbers for which there is meaningful addition, subtraction, multiplication and division.

In some situations, numbers at ordinal level can be treated as having an interval and in others they cannot. It depends on the coding assigned to the attributes of ordinal level variables.

The interval level is a much higher level of measurement than the nominal level and even higher than the ordinal level. At this level, the numbers of the distance between attributes that can be meaningfully added and subtracted.

This means that there is a fixed distance between the temperature levels — as when a ruler is used to measure the distance between two points using the same distance scale.

This means that numbers measured at the interval level cannot be multiplied or divided in a meaningful way. At the highest level of measurement is the ratio. A true zero exists for the numbers at this level.

This means that numbers can be multiplied and divided as well as added and subtracted in a meaningful way. For instance, in the Fahrenheit system for measuring temperature, zero is not the absence of heat.

Thus, measurement is at the interval level because the distance between points is fixed and on the same scale. However, in the Kelvin system for temperature measurement there is an absolute zero at which molecular action ceases.

This means that the Kelvin scale is at the ratio level of measurement. Variables at higher levels of measurement can be transformed into lower levels of measurement. This is the case with grouping the ratio level variable of income in Table 3.

Here the variable measured at ratio level was transformed into a variable measured at ordinal level. This process could be continued by classifying the income data into two groups labelled Yes and No, where these two categories would be those with income below or above a certain amount of income say the average income.

This transformation would re-code income data into a nominal level variable. The analysis of demographic information can be of a descriptive nature, as in the case of the estimation of percentages, measures of central tendency and dispersion discussed later.

It may also be of an inferential nature. In that case, demographic analysis is concerned with relationships either between groups in or characteristics of population, as in the case of correlation and regression, briefly discussed later.

Statistical methods should be consistent with the nature of the data, as categorical and ranked data may require different methods of analysis. For example, the estimated population of the world was 6, million people in mid United Nations This is just one count.

Other counts may relate to the population of different regions of the world, for example, that of Asia was 4, million and Europe million. On a smaller scale, counts may consist of data based on a few observations, such as the hypothetical data on daily income dollars of 30 people in Table 3.

The daily income of these 30 people can be summarised into income groups that cover the range of individual incomes. In making this conversion, data at the interval level is transformed into ordinal level data.

In this instance, each individual is classified according to their daily income and counted as a member of the relevant income group. The result is given in Table 3.

However, the size of each income group could be different and there could be a smaller or larger number of income groups. Nevertheless, the sum of all groups would continue to be Such a distribution is called a frequency distribution because it counts the number of observations frequency in each group.

Three features of each group need to be considered, when estimates are made from the frequency distribution: In fact, the upper limits are just less than 30, 50, 70, 90 and respectively. As stated, in this example the width interval is the same for all, except the first, income groups but groups may have unequal intervals.

The data presented in Table 3. In this example, the ungrouped data are measured at the ratio level while in their grouped form they are measured at the ordinal level. This converted into a percentage is 0.

Accordingly, the proportion of the world population living in Asia was 0. In other words, there were close to 60 people living in Asia out of every in the world. Frequency distributions can be converted into proportional or percentage frequency distributions by dividing the frequency in each group by the total number, as illustrated in Table 3.

A hypothetical distribution of males and females by income group is shown in Table 3. Such a table is called a bivariate table as it involves two variables: It can also be called a five by two table since it crossclassifies five income values by two sex values.

In this case, income is at the ordinal level of measurement and sex is at the nominal level. There are three ways of calculating percentages from a bivariate table, as shown in Tables 3.

Percentages have been calculated separately for females and males in Table 3. The percentage total in each column is The last column has the percentage distribution of all persons according to income.

It is the same as that given in the fourth column of Table 3. The percentage distribution of males and females can also be estimated for each income group as in Table 3. Each row adds to The last row in the table shows that Totals for columns may not add due to rounding Table 3.

Totals for rows may not add due to rounding All persons Totals in columns and rows may not add due to rounding Each cell of Table 3. Relative measures can also be 3.

United Nations No. Relative measures are similar, but each has a distinct meaning. A ratio is simply a number divided by another. However, in demographic analysis a ratio is usually the quotient of two groups of people with different characteristics in the same population or the quotient of one variable by another.

As stated earlier, in there were 6, million people in the world; the number of males was 3, and females 3, million United Nations The ratio of males to females was: The number of births in China during was estimated as Accordingly, the rate of births in China during was: It relates a number of events or some other demographic variable to the average population during the specified period of time, usually the mid-period population.

In other words, a rate is the number of events or some other demographic variable occurring during a given period of time divided by the population at risk of the occurrence of those events or the population to which the demographic variable relates to.

For example, the birth rate is the number of births from a given population divided by the population exposed to the risk of having those births. Rates of births to population in Egypt and the United States are presented in Table 3.

Some rates may be expressed per person, in percentages, per thousand people or even per hundred thousand depending on the size of the number of events in relation to that of the relevant population.

Although the concept of a rate is clear, it is often difficult or practically impossible to get an exact measure of the population at risk to the occurrence of the particular event.

For instance, only females in their childbearing years are 28 3 Some Basic Statistical Measures Table 3. Some may die during the period — in a given area — some may move away and other move in.

How can the population exposed to the risk of giving birth in that area be defined and measured? This problem is usually solved by using the midyear year or period of time population as an approximation.

This solution is based on the assumption that births and deaths occur evenly throughout the year, so that the midyear population is a measure of the average of the reference population during the year.

The resulting rate is called a central rate. Usually, the use of the midyear population is adequate to get reasonable results. However, if the population is growing at a substantial rate throughout the year, it might be more adequate to use the average of the population at given intervals during the year.

A distinction can also be made between central rates and probabilities. In a central rate the denominator is the population at the mid-point of the time period say the middle of the year. It is meant to represent the average population during the time period.

In a probability, the denominator is the population at the beginning of the time period. This is thought to correspond more closely to the population at risk of the occurrence of an event during the time period.

The distinction between central rates and probabilities is somewhat fuzzy because of the movement of people into and out of an area. For example, if age-specific rates are considered, a true single-year probability can be calculated using the population of the area at the beginning of the year and the number of deaths that took place during the year to members of the population, at the beginning of the year, for each age cohort.

However, some deaths will be missed by the death registration system for the area because they relate to people who moved out of the area during the year. Further, some deaths will be improperly included because they refer to people who moved into the area during the year.

Consequently, it is difficult if not impossible to estimate true probabilities for a variety of demographic measures. The term rate is used loosely in demography, as it is elsewhere.

Many measures called rates are really ratios. A growth rate, for example, is a ratio of population change over a time period to the population at the beginning of the time period. The most commonly used are the arithmetic mean also referred to as the mean, median and mode.

The mean, median and mode can be used with variables measured at the interval or ratio levels, and some times at the ordinal level. If variables are measured at the ordinal or nominal level, the mode is generally the most meaningful measure of central tendency.

Two other less frequently estimated means are also discussed: As their names suggest, they were designed to use variables measured at the interval and ratio levels.

The estimated mean of the income data in Table 3. It is assumed that the individual incomes, or any other variable in the calculation of the mean, are evenly distributed within each group, and the mid-point in the group is taken as the average value of xi for the whole group.

An example of the computations involved in the estimation of the mean in grouped data Table 3. The mid-point xi is multiplied by the frequency for that group in column 2 , i. If the width of the last group is open ended, that is, the upper limit is not specified, then the estimation of the mean will depend upon the assumption regarding the length of that interval.

For example, if in Table 3. The AM may be affected by extreme values. For instance, in a series of six numbers 23, 25, 30, , 20, and 24, the AM is 62, despite the fact that all but one values lie between 20 and The following measures of central tendency are not affected by extreme values to the same extent as the AM.

For a given set of numbers x1, x2,. The value of n may be any number from 2 onwards. An easier way to calculate the n th root is through logarithms. Two types of logarithms are: The former are referred to as logarithms log and the latter as natural logarithms LN or ln.

The LN of is 4. Antilogarithms enable the conversion of a logarithm back into the original number. The antilogarithm of log is 10x and that of LN is ex.

Most calculators have log, 10x, LN or ln and ex keys. The following rules apply to both log and LN: In general, the following relationship holds for any series of numbers: Usually, GM and HM are not calculated for grouped data.

In other words, the median divides the ordered set into two equal parts: Accordingly, the first step in the estimation of the median for the figures in Table 3. The median daily income is The p is 0.

The median group is identified by halving the total frequency n. This is the first group that has a 3. The value of L is the lower limit of the median group, i is the width, and f is the frequency. C is the cumulative frequency of the group preceding the median group and n is the total of the frequencies for all groups.

Ungrouped data give more precise estimates of both AM and the median, but demographic data are generally available in grouped formats. Depending on the nature of the analysis the median may be preferred to the AM.

The median is often used in place of the mean when data are highly skewed that pulls the mean way from the bulk of the observations. The median is not affected by the skewness of the distribution of observations.

In grouped data, it is the group that has the largest frequency if the class intervals are about the same. Some distributions have a single mode while others may have two or more modes. In this example, the mode is 30—34 years age group, as this has the largest number of births recorded.

It is an example of a distribution with one mode uni-modal distribution. Japan An example of a distribution with two modes bi-modal distribution is the number of Japanese females in the labour force by age Japan in Fig.

In this instance, there were two modes: There may be distributions with more than two modes. The value of the mode is that corresponding to the top of the hump.

This is also the median that divides the distribution into two equal halves. The AM of this distribution also coincides 3. This distribution rarely occurs in the real world. However, it is an important component of the theory that underlies statistical inference.

A non-symmetrical distribution is called a skewed distribution. There are two types of skewed distributions: In a positively skewed distribution the value of both the median and the mean AM are larger than the mode.

In a negatively skewed distribution they are both smaller than the mode Figs. The properties of these three types of distributions can be summarised as follows: These properties are used in developing measures of skewness.

The variance and the standard deviation can be estimated for data at the interval and ratio levels and sometimes for data at the ordinal level. They should not be used with data at the nominal level unless the data have been transformed using dummy coding.

Quantiles are essentially measures of data at interval and ratio levels that have been transformed into ordinal categories. The equations to calculate the variance VAR and the standard deviation SD for a set of n numbers x1, x2,.

These differences are squared multiplied by themselves column 3 to convert them into positive values. The standard deviation SD is the square root of the variance. The standard deviation can be viewed as the average expected error that results from using the mean AM to predict individual values of the variable in question.

For example, if AM of This is an important concept to remember because it forms a basis to evaluate a regression model, a topic that is discussed later on. The denominator is sum of frequencies n minus 1.

These two measures are Although the median is usually considered a measure of central tendency, the median is a quantile that divides a series into two equal parts. In addition to the median, quartiles, quintiles and deciles are some of the other commonly used quantiles.

They represent the partition of a series into four quartiles, five quintiles and ten deciles equal parts. The number of positional points required is one less than the partitions, because the last positional point is the highest value of the series.

Thus, there is no need to calculate the fourth quartile or the fifth quintile or the tenth decile as they are the last value of the ascending series. Quantiles for Ungrouped Data The identification of the quantile points involves first the selection of the number of partitions required.

The series in Table 3. The median that divides the series into two equal parts has already been shown as lying between The median is, by definition, equal to the second quartile Q2.

The lowest quartile point Q1 is positioned at Similarly the third quartile point Q3 divides the second half of the series into two equal parts and is located at The fourth quartile point Q4 is The five quintile points QN1—QN5 are as indicated above.

The ten decile points D1—D10 , are noted above. Quantiles for Grouped Data The estimation of quantiles in frequency distributions starts by the identification of the interval that contains the quantile group.

The procedure is essentially the same as that for the calculation of median described earlier. The first step involves the identification of the particular quantile group.

This depends on whether quartiles, quintiles or deciles are being calculated. It is the same as Eq. Income data from Table 3. Once a particular quantile group is identified the values of L, i, f, n and C are substituted in Eq.

The following examples are concerned with the estimation of the location values for the third quartile Q3 , the second quintile QN2 and the sixth decile D6 from Table 3.

Frequency fi 2 8 10 6 4 30 Cumulative frequency Ci 2 10 20 26 To estimate Q3, the corresponding value of p is 0. Multiplying this by n 30 equals The fourth column of Table 3. Substituting these values in Eq.

To estimate the second quintile QN2 , the value of p is 0. From the fourth column of Table 3. Substituting the above values in Eq. To estimate D6, the value of p from Table 3. This value multiplied by n 30 equals The comparison of the values of the location points for various quantiles of the grouped and ungrouped data indicates that the estimated quantiles are similar.

The first column identifies portions of the distribution expressed as percentages that are included in the particular quantile. The second column gives the range of location points that contain the particular portion, and the third column shows the range of values for each quantile using the hypothetical income data.

This column is based on the last column of Table 3. Similar interpretations can be given to the quintiles that divide the series into five equal parts and deciles that divide it into ten equal parts.

A question that arises often is the degree of inequality among the quantiles. One of the most commonly used measures of inequality is the Gini Coefficient. This measure has been employed to measure inequalities in income, wealth, health and education and other characteristics.

Essentially, it involves numbers at the interval or ratio levels that have been transformed into ordinal data quantiles. The third column is based on the last column of Table 3. However, reality is often different.

In the square, in Fig. The diagonal line divides the square in two equal triangles. The triangle formed by the diagonal on the right side of the square consists of two parts A and B, where A comprises of the area between the 44 3 Some Basic Statistical Measures Fig.

The Gini Coefficient G is defined as: The higher the coefficient the greater the inequality between the distributions of the variables X and Y. The Gini Coefficient is often expressed as a percentage.

An approximation of the coefficient can be estimated using the following equation: United Kingdom, Table 3. Columns 2 and 3 were taken from the survey report United Kingdom Total estimated income for all households in each quintile is stated in column 4.

An alternative method that gives the same answer is: Other inequality measures are also used. Among them, ratios of high and low quintiles are often used to measure inequality, say, between the highest and lowest quintiles.

This indicates that the inequality ratio between Quintile 1 and 5 was: Conceptually, it is related to the Gini Coefficient. As such, essentially, it also measures interval and ratio level data that have been transformed into ordinal data.

It is calculated as: This index varies from 0, when both populations are identical, to 1, when both populations are completely dissimilar. The characteristic i may be any population characteristic such as age, education, occupation or location.

Unlike ID that measures the absolute differences, the IRD measures the relative difference, where population in the denominator Bi is taken as the standard. Both indexes can be calculated for a number of populations by substituting in turn the Ai values with corresponding values for other populations.

Japan, Spain and Egypt United Nations Both indexes for Egypt were substantially higher than those for Spain, thereby indicating that the age distribution of Spain was closer to that of Japan.

Earlier, in Table 3. In this example, the age of brides and bridegrooms in 50 hypothetical marriages is given in Table 3. Columns 1 and 4 give the marriage number i. The related age of the bride yi is in columns 2 and 5 and that of the bridegroom xi in columns 3 and 6.

These data are measured at the ratio level, so both correlation and regression are appropriate analytical tools to use. An association is apparent in Fig. The age of the bride yi goes from its smallest value of 18 years on the horizontal axis to its highest value of 27 years along the same axis; the values of the age of the bridegroom xi also becomes larger from its lowest value of 20 on the vertical axis to its highest value of 43 years of age.

As the values of xi get older the values of yi also tend to get older: However, this positive linear relationship between xi and yi is not perfect: If the linear relationship between xi and yi was perfect all the plotted points 1 2 0—14 United Nations, Table 7a Age years 3 In statistical terms, this association is called correlation.

An indicator of correlation is the correlation coefficient r calculated as: The variables in Eq. Data presented in Tables 3. The from Table 3. In a positive correlation an increase in one variable is associated with an increase in the other, while in a negative correlation an increase in one corresponds to a decrease in the other variable.

In the above example the correlation was positive. Another coefficient related to r is the coefficient of determination R as: In this example, the coefficient of determination is 0. This explanation is in terms of the mean age of the bridegrooms.

The coefficient of determination measures the improvement or lack thereof a regression model provides relative to using the mean of the variable to be predicted.

It should be kept in mind that if the mean of the variable to be predicted is highly accurate the standard deviation is very low, not much might be gained by the introduction of a new variable in the prediction process: Conversely, the standard deviation of a variable whose values are to be predicted might be extremely high.

In that case, the introduction of another variable to predict the value of the variable via regression analysis may result in a low coefficient of variation. However, such a regression may still offer a great deal of improvement over the use of the mean of that variable as a predictor.

It may also be the case that when the variation of the variable to be predicted is considerably high that a regression model ends up with a high coefficient of determination; but it is still not a good predictor of the variable in question.

In such cases, a transformation of the data may be needed Swanson It is advisable to be keenly aware of means and standard deviations of variables when considering and evaluating regression models.

One way of assessing the 52 3 Some Basic Statistical Measures relationship between the mean and its standard variation is the estimation of the coefficient of variation CV as: The coefficient of variation can be used for purposes of comparison since it provides a measure of variation relative to the mean.

It is also important to graph relationships Anscombe and to be aware of the assumptions underlying regression, the consequences of violating them, and how to overcome these violations Fox It states that low income households spend a greater proportion of their income on food than the richer households.

This correlation between household income and expenditure on food has been tested empirically. Each correlation coefficient is associated with two regression coefficients, one measure the impact of variable of xi on variable yi and the other determines the impact of yi on xi.

These may be referred to as b1 and b2 respectively, and are estimated using Eqs. The two regression coefficients were estimated from data in Tables 3. Interpretation of the b1 is that one unit increase in xi will result in 0.

The correlation coefficient gives an indication of association but not of cause and effect between the two variables. Regression coefficients imply that there is an independent variable cause and a dependent variable effect: These parameters are also known as the intercept i.

The slope is in fact identical to the regression coefficient as indicated in Eqs. In geometric terms, this equation can be envisaged as a line with coordinates X and Y. A line can be determined by two points A and B with coordinates x1, y1 and x2, y2.

The gradient or slope of the line represents the relationship between X, the independent variable, and Y the dependent valuable. However, if Y and X assume different values at the origin, and unless the line is parallel to Y, the line is bound to intercept the Y axis and this intercept is needed to estimate the value of Y given a value of X.

The graph in this box can be used as an illustration. The intercepts a1 and a2 for linear models corresponding with the regression coefficients b1 and b2 are: A linear regression model can have more than one independent variable.

In a bivariate regression model when there is only one independent variable, the regression coefficient is concerned only with the relationship between that variable and the dependent one.

However, in a multiple regression model where there are more than one independent variables, the model cannot just assess the relationship between each of the independent variables and dependent variable.

It needs to take cognisance of the other independent variables. The regression coefficients for each independent variable are estimated while controlling the explanatory power of the other independent variables.

Accordingly, these coefficients are known as partial regression coefficients. In multiple regression one of the issues is the possibility that in addition to the relationship between the independent and the dependent variables, there is a also a relationship between two or more of the independent variables.

In some cases, even though there is a good relationship between an independent and the dependent variable, the addition of that independent variable to the model may not add to the explanatory value of the model, because of this factor.

The coefficient of multiple determination R2 like its counterpart in the bivariate linear regression model measures the variation in the dependent variable explained by the predictive power of the independent variables: To illustrate the use of multiple regression model an additional independent variable is provided in Table 3.

The computations involved in the estimation of multiple regression models are complicated and can be facilitated by the use of a software package such as the Excel which has a subroutine for multiple regressions Triola References 57 Table 3.

The value of R2 for this model is 0. Graphs in statistical analysis. The American Statistician, 27, 17— Regression diagnostics Quantitative applications in the social sciences, Vol.

Sociological Methodology, 15, 1— Portal site of official statistics of Japan. The dimensions of racial segregation. Social Forces, 67 2 , — On the theory of scales of measurement.

Science, , — Advancing methodological knowledge within state and local demography: Population Research and Policy Review, 23, — Elementary statistics using excel 3rd ed. Family spending, edition.

Chapter 4 Elements of Demographic Analysis 4. This follows the description of the field of demography and the nature of related data Chaps. In this chapter some of the five generic aspects of demography a population size, b geographic distribution, c composition, d components of change births, deaths and migration, and e determinants of change are discussed.

These include the concepts of the balancing equation, demographic stocks and flows, various types of rates and ratios, standardisation and graphical presentation of demographic data. Statistics from a variety of countries are used for illustrative purposes.

This model may take the following form: Usually, the value of n is 1 year, but it can be more or less in duration. Accordingly, PG can be defined as: In a given population, if the number of births exceeds the number of deaths, NIt!

Apart from a few countries in Europe, the general trend is for positive natural increase. In some others, such as China and Japan, it is negligible as a proportion of the total population.

At the sub-national level equation, the counterpart of Eq. The data given in this table are the sum of figures for four quarters of the year NDM is zero at the national level because movements of population within a country cancel each other.

Urban areas, and particularly large cities, attract people from rural areas. This movement of people from rural to urban area is known as urbanisation. The births component of natural increase is discussed in more detail in the chapter on fertility Chap.

International and domestic migration are discussed in Chap. The table shows that net international migration was the biggest component of population growth in all States and Territories.

Three of them New South Wales, South Australia and the Australian Capital Territory experienced a net loss of population through domestic migration and the others gained. Of course, the sum of the net domestic migration was zero.

A more precise measure is the net increment in the population from a given date to another. Generally, the rate of population growth is estimated on an annual basis: An illustration is provided by United States data in Sect.

If this is not the case, it is important to ensure that that the value of n is calculated to two or more decimal places, and not just the nearest whole number. As an example, the population of India on 31 December is interpolated.

Therefore, the calculations were based on Pmid The result would be identical, if Pmid is the starting point and n is 9. Substituting the value of r for India 0.

To facilitate the use of Eqs. For instance, the population stock of the United States in mid was As noted in Chap. These are also called vital events. In the United States data in Sect.

There are two types of vital events: Births, deaths and migration both international and domestic belong to the first type of vital events. Marriages and divorces, and entry to and exit from the labour force are examples of the second type of vital events.

The cross-sectional approach is concerned with the collection and analysis of data concerned with population size, its composition and characteristics at a particular point, or period, of time.

Most demographic data such as the census and registration of vital events are collected using this approach. Another approach involves selecting a group of people who share a common characteristic such as year of birth referred to as the birth cohort and record and analyse their experiences over time.

This is called the longitudinal approach. Alternatively, a time-series of cross sectional data may be used to follow a particular cohort of the population. Often, it is not convenient to wait that long.

To overcome this time-lag, synthetic measures have been developed for variables such as fertility and mortality. These measures may use current patterns of experience to assess the potential longitudinal experience, on the assumption that the current population stock, flows and characteristics stayed constant.

The total fertility rate Chap. They usually involve the count of some particular vital event over a specified period of time divided by the average population during the same period.

Crude rates are defined as: The crude rates for vital events mentioned in Eq. The denominator remains as Pt! Similar rates can also be calculated for various components of population growth mentioned in Eq.

The denominator for each rate is the same: Characteristic-specific rates relate vital events to characteristic-specific groups in the population that experience such events.

The general formula for the i-specific rate is: Characteristic-specific rates can be calculated by specifying one characteristic such as age, or two characteristics such age and sex or even multiple characteristics.

These rates are discussed in more detail in subsequent chapters. It is sometimes referred to as the masculinity ratio, and is calculated by dividing the number of males by the number of females.

The sex ratio can also be expressed as a femininity ratio by taking the number of females in the numerator and males in the denominator. The sex ratio can be estimated for the total population or for any segment of the population with characteristic i.

Sex ratio SRit for characteristic i at time t is defined as: Usually, characteristic i refers to the age, however, other characteristics can also be used. The declining trend in sex ratio by age is evident in both countries.

It is a well-known phenomenon due to the comparatively more frequent deaths among males than females, particularly in the older ages. In most populations, the sex ratio at birth fluctuates around an average of 1.

The number of births in Canada and Egypt United Nations provide an example of estimation of sex ratio at birth: Male live births during the year Bm t! Brazil and Italy, Source: This ratio relates the number of children both males and females added together aged less than 5 years to women in their reproductive period at a given point in time.

Usually, the reproductive period of females is considered to be either 15—44 or 15—49 years of age. This ratio is a crude indicator of the level of fertility.

In the following example, data for Brazil and Italy supply the basis for the calculation of CWR for both countries United Nations These figures indicate that Brazilian women had, on average, more children than their Italian counterparts.

These ratios are also expressed per 1, women. In this example, the reproductive period was defined as 15—44 years of age. Obviously, the ratios would be somewhat lower if the age group was extended to 49 years.

Dependents consist of two groups of people: Independents are considered to be the persons 15—64 years of age. The dependency ratio at time t is defined as: This ratio is not Pt necessarily an index of economic dependency.

The sum of these two ratios is the equivalent to the dependency ratio. The age distributions for Brazil and Italy are used to illustrate the calculation of dependency ratios and their components United Nations

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03.03.2018 - The passage of the National Historic Preservation Act in established the National Register, of the more than one million properties on the National Register,80, are listed individually. Yet, other sample surveys collect data on a range of human activities including how people use their time Australia Ccleaner free download full version for windows 7 ... Printers published the tracing in at least three formats, [11] [48] which together enabled the Plan to be widely distributed for the first time, the printers added to each of the reproduced tracings a copy of a message that a survey assistant had sent to the survey's superintendent. The multistage sampling usually involves the random selection of a higher order unit such as a region. Achieved characteristics are also used and include:

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29.01.2018 - It is commonly used in demography as well as other disciplines, such as sociology, economics and epidemiology. At the time, the Patawomeck and the Doeg lived on the Virginia side, as well as on Theodore Roosevelt Island, Native inhabitants within the present-day District of Columbia included the Nacotchtank, at Anacostia, who were affiliated with the Conoy. They may collect the data from primary sources through censuses and surveys or retrieve data from other agencies, individuals or corporations. Ccleaner free download for linux ubuntu - New piri... This model may take the following form: A birth is the result of a pregnancy that involves the complete expulsion or extraction of the product of a pregnancy regardless of the duration of pregnancy. Sampling was first used in a 1.

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16.03.2018 - Each individual item has an equal chance of being selected and given equal value. Projection of the population of Ryde Municipality, —, using the cohort-change method. Practitioners of urban planning are concerned with research and analysis, strategic thinking, architecture, urban design, public consultation, policy recommendations, implementation and management. Ccleaner free download for windows 8 softonic - Fr... Estimation of the expected number of events in two hypothetical populations subjected to the same age-specific rates. Data presented in Tables 3.



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However, the Constitution does not specify a location for the capital, on July 9,, Congress passed the Residence Act, which approved the creation of a national capital on the Potomac River. The exact location was to be selected by President George Washington, formed from land donated by the states of Maryland and Virginia, the initial shape of the federal district was a square measuring 10 miles on each side, totaling square miles.

Two pre-existing settlements were included in the territory, the port of Georgetown, Maryland, founded in, many of the stones are still standing. Geographic coordinate system — A geographic coordinate system is a coordinate system used in geography that enables every location on Earth to be specified by a set of numbers, letters or symbols.

The coordinates are chosen such that one of the numbers represents a vertical position. A common choice of coordinates is latitude, longitude and elevation, to specify a location on a two-dimensional map requires a map projection.

The invention of a coordinate system is generally credited to Eratosthenes of Cyrene. Ptolemy credited him with the adoption of longitude and latitude. Ptolemys 2nd-century Geography used the prime meridian but measured latitude from the equator instead.

Mathematical cartography resumed in Europe following Maximus Planudes recovery of Ptolemys text a little before, in, the United States hosted the International Meridian Conference, attended by representatives from twenty-five nations.

Twenty-two of them agreed to adopt the longitude of the Royal Observatory in Greenwich, the Dominican Republic voted against the motion, while France and Brazil abstained.

France adopted Greenwich Mean Time in place of local determinations by the Paris Observatory in, the latitude of a point on Earths surface is the angle between the equatorial plane and the straight line that passes through that point and through the center of the Earth.

The equator divides the globe into Northern and Southern Hemispheres, the longitude of a point on Earths surface is the angle east or west of a reference meridian to another meridian that passes through that point.

All meridians are halves of great ellipses, which converge at the north and south poles, the prime meridian determines the proper Eastern and Western Hemispheres, although maps often divide these hemispheres further west in order to keep the Old World on a single side.

To completely specify a location of a feature on, in, or above Earth. Earth is not a sphere, but a shape approximating a biaxial ellipsoid. It is nearly spherical, but has an equatorial bulge making the radius at the equator about 0.

Urban planning — Urban planning is also referred to as urban and regional planning, regional planning, town planning, city planning, rural planning or some combination in various areas worldwide.

It takes many forms and it can share perspectives and practices with urban design, urban planning guides orderly development in urban, suburban and rural areas. Practitioners of urban planning are concerned with research and analysis, strategic thinking, architecture, urban design, public consultation, policy recommendations, implementation and management.

Urban planners work with the fields of architecture, landscape architecture, civil engineering. Early urban planners were often members of these cognate fields, today urban planning is a separate, independent professional discipline.

The discipline is the category that includes different sub-fields such as land-use planning, zoning, economic development, environmental planning. There is evidence of planning and designed communities dating back to the Mesopotamian, Indus Valley, Minoan.

Archeologists studying the ruins of cities in these areas find paved streets that were out at right angles in a grid pattern. The idea of a planned out urban area evolved as different civilizations adopted it, beginning in the 8th century BCE, Greek city states were primarily centered on orthogonal plans.

The ancient Romans, inspired by the Greeks, also used orthogonal plans for their cities, city planning in the Roman world was developed for military defense and public convenience.

The spread of the Roman Empire subsequently spread the ideas of urban planning, as the Roman Empire declined, these ideas slowly disappeared. However, many cities in Europe still held onto the planned Roman city center, cities in Europe from the 9th to 14th centuries, often grew organically and sometimes chaotically.

But many hundreds of new towns were built according to preconceived plans. Most of these were realized from the 12th to 14th centuries, from the 15th century on, much more is recorded of urban design and the people that were involved.

In this period, theoretical treatises on architecture and urban planning start to appear in which questions are addressed and designs of towns. Planning and architecture went through a shift at the turn of the 20th century.

The industrialized cities of the 19th century grew at a tremendous rate, the pace and style of this industrial construction was largely dictated by the concerns of private business.

In, his brother Pierre Joseph died at the age of six and he studied art at the Royal Academy in the Louvre, as well as with his father at the Royal Academy of Painting and Sculpture. He arrived in at the age of 23, and served as an engineer in the Continental Army with Major General Lafayette.

He was commissioned as a captain in the Corps of Engineers on April 3, to rank from February 18,, despite his aristocratic origins, LEnfant closely identified with the United States, changing his first name from Pierre to Peter.

He was wounded at the Siege of Savannah on October 9, and he recovered and became a prisoner of war at surrender of Charleston, South Carolina on May 12, He was exchanged in November and served on General George Washingtons staff for the remainder of the Revolutionary War, LEnfant was promoted by brevet to Major of Engineers on May 2,, in recognition of his service to the cause of American liberty.

He was discharged when the Continental Army was disbanded in December, after the war, LEnfant designed the badge of the Society of the Cincinnati, an organization of former officers of the Continental Army, shaped as an eagle, at the request of Washington.

He was sent to France to have made for members of the Society. He also designed furniture and houses for the wealthy as well as coins and medals and he was also a friend of Alexander Hamilton.

Included in the new district were the port towns of Georgetown. LEnfant arrived in Georgetown on March 9,, and began his work, Washington arrived later on March 28, to meet with LEnfant and the Commissioners for several days.

On June 22, LEnfant presented his first plan for the city to the President. On August 19, he appended a new map to a letter that he sent to the President, President Washington retained a copy of one of LEnfants plans, showed it to the Congress, and later gave it to the three Commissioners.

Presidency of George Washington — The presidency of George Washington, began on April 30,, when he was inaugurated as the 1st President of the United States, and ended on March 4, Washington took office after the —89 presidential election, the nations first quadrennial presidential election, as specified by the newly ratified Constitution, the President was chosen by the Electoral College.

In this election, the method for selecting electors was decided by each state legislature—by public vote in some states, each elector was given two votes to cast for President. Washington received the support of one of the electors, each of whom cast one of the two ballots for him.

John Adams, who received 34 votes, was the runner-up and was named vice president. President Washington was re-elected as President, again unanimously, in, in, he refused to run for a third term, establishing the customary policy of a maximum of two terms for a president, which later became law by the 22nd Amendment to the Constitution.

Washington reluctantly accepted the presidency, and he never enjoyed being President, nonetheless, he proved an able administrator. An excellent delegator and judge of talent and character, he held cabinet meetings to debate issues before making a final decision.

In handling routine tasks, he was systematic, orderly, energetic, solicitous of the opinion of others but decisive, intent upon general goals and his leadership guaranteed the survival of the United States as a powerful and independent nation, and set the standard for future presidents.

Washington was inaugurated as the first President of the United States on April 30,, near New York Citys Wall Street and he was sworn in by Robert Livingston who administered the presidential oath of office.

Borrowing a British robe in which the British monarch would address Parliament annually and he insisted on having Barbados Rum served after the swearing in ceremony. Washingtons second inauguration occurred in the Senate Chamber of Congress Hall in Philadelphia, Pennsylvania on March 4, and he was sworn in by Associate Justice William Cushing, who also administered the oath of office.

Washington faced financial troubles then, yet he initially declined the salary, upon taking office, Washington initially focused on the establishment of the federal judiciary and executive departments.

When Washington assumed office, the government of the United States had not yet been developed, aside from the constitutionally established offices, no other agencies existed and no courts had yet been established.

Instead of focusing on the branch, Washingtons first acts were to establish the judiciary. Under the Supreme Court, the Judiciary Act created 13 judicial districts within the 11 states that had ratified the Constitution.

The president directs the executive branch of the government and is the commander-in-chief of the United States Armed Forces. The president is considered to be one of the worlds most powerful political figures, the role includes being the commander-in-chief of the worlds most expensive military with the second largest nuclear arsenal and leading the nation with the largest economy by nominal GDP.

The office of President holds significant hard and soft power both in the United States and abroad, Constitution vests the executive power of the United States in the president. The president is empowered to grant federal pardons and reprieves.

The president is responsible for dictating the legislative agenda of the party to which the president is a member. The president also directs the foreign and domestic policy of the United States, since the office of President was established in, its power has grown substantially, as has the power of the federal government as a whole.

However, nine vice presidents have assumed the presidency without having elected to the office. The Twenty-second Amendment prohibits anyone from being elected president for a third term, in all,44 individuals have served 45 presidencies spanning 57 full four-year terms.

On January 20,, Donald Trump was sworn in as the 45th, in, the Thirteen Colonies, acting through the Second Continental Congress, declared political independence from Great Britain during the American Revolution.

The new states, though independent of each other as nation states, desiring to avoid anything that remotely resembled a monarchy, Congress negotiated the Articles of Confederation to establish a weak alliance between the states.

Out from under any monarchy, the states assigned some formerly royal prerogatives to Congress, only after all the states agreed to a resolution settling competing western land claims did the Articles take effect on March 1,, when Maryland became the final state to ratify them.

In, the Treaty of Paris secured independence for each of the former colonies, with peace at hand, the states each turned toward their own internal affairs. Prospects for the convention appeared bleak until James Madison and Edmund Randolph succeeded in securing George Washingtons attendance to Philadelphia as a delegate for Virginia.

It was through the negotiations at Philadelphia that the presidency framed in the U. The first power the Constitution confers upon the president is the veto, the Presentment Clause requires any bill passed by Congress to be presented to the president before it can become law.

Once the legislation has been presented, the president has three options, Sign the legislation, the bill becomes law. Veto the legislation and return it to Congress, expressing any objections, in this instance, the president neither signs nor vetoes the legislation.

History of Washington, D. Originally inhabited by an Algonquian-speaking people known as the Nacotchtank, the site of the District of Columbia along the Potomac River was first selected by President George Washington, the city came under attack during the War of in an episode known as the Burning of Washington.

Upon the governments return to the capital, it had to manage reconstruction of public buildings, including the White House. The McMillan Plan of helped restore and beautify the downtown area, including establishing the National Mall, along with numerous monuments.

Unique among cities with a percentage of African Americans, Washington has had a significant black population since the citys creation. Since the city government was run by the U.

This situation persisted for decades, the city was segregated in certain facilities until the s. Following World War II, many whites moved out of the citys central and eastern sections to newer, affordable suburban housing.

The assassination of Martin Luther King, Jr. A rising economy and gentrification in the late s and early s led to revitalization of many downtown neighborhoods, article One, Section 8, of the United States Constitution places the District under the exclusive legislation of Congress.

Throughout its history, Washington, D. The District of Columbia Home Rule Act provided the government more control of affairs, including direct election of the city council.

Archaeological evidence indicates Native Americans settled in the area at least 4, years ago, Early European exploration of the region took place early in the 17th century, including explorations by Captain John Smith in At the time, the Patawomeck and the Doeg lived on the Virginia side, as well as on Theodore Roosevelt Island, Native inhabitants within the present-day District of Columbia included the Nacotchtank, at Anacostia, who were affiliated with the Conoy.

Another village was located between Little Falls and Georgetown, and English fur trader Henry Fleet documented a Nacotchtank village called Tohoga on the site of present-day Georgetown.

Established by a resolution of the Congress on June 14,, the Continental Army was supplemented by local militias and troops that remained under control of the individual states or were otherwise independent.

General George Washington was the commander-in-chief of the army throughout the war, most of the Continental Army was disbanded in after the Treaty of Paris ended the war.

The 1st and 2nd Regiments went on to form the nucleus of the Legion of the United States in under General Anthony Wayne and this became the foundation of the United States Army in The Continental Army consisted of soldiers from all 13 colonies, and after, when the American Revolutionary War began at the Battles of Lexington and Concord on April 19,, the colonial revolutionaries did not have an army.

As tensions with Great Britain increased in the leading to the war. Training of militiamen increased after the passage of the Intolerable Acts in, colonists such as Richard Henry Lee proposed forming a national militia force, but the First Continental Congress rejected the idea.

On April 23,, the Massachusetts Provincial Congress authorized the raising of an army consisting of 26 company regiments. New Hampshire, Rhode Island, and Connecticut soon raised similar, on July 18,, the Congress requested all colonies form militia companies from all able bodied effective men, between sixteen and fifty years of age.

It was not uncommon for men younger than sixteen to enlist as most colonies had no requirement of consent for those under twenty-one. Four major-generals and eight brigadier-generals were appointed by the Second Continental Congress in the course of a few days, after Pomeroy did not accept, John Thomas was appointed in his place.

As the Continental Congress increasingly adopted the responsibilities and posture of a legislature for a sovereign state, as a result, the army went through several distinct phases, characterized by official dissolution and reorganization of units.

Soldiers in the Continental Army were citizens who had volunteered to serve in the army, early in the war the enlistment periods were short, as the Continental Congress feared the possibility of the Continental Army evolving into a permanent army.

The army never numbered more than 17, men, turnover proved a constant problem, particularly in the winter of —77, and longer enlistments were approved. Major General Philip Schuylers ten regiments in New York were sent to invade Canada, the Continental Army of, reorganized after the initial enlistment period of the soldiers in the army had expired.

Despite attempts to broaden the recruiting base beyond New England, the army remained skewed toward the Northeast both in terms of its composition and of its geographical focus. This army consisted of 36 regiments, most standardized to a battalion of men strong and formed into eight companies.

Enlistment terms extended to three years or to the length of the war to avoid the crises that depleted forces. American Revolutionary War — From about the American Revolution had led to increasing philosophical and political differences between Great Britain and its American colonies.

The war represented a culmination of these differences in armed conflict between Patriots and the authority which they increasingly resisted. This resistance became particularly widespread in the New England Colonies, especially in the Province of Massachusetts Bay.

The Massachusetts colonists responded with the Suffolk Resolves, establishing a government that removed control of the province from the Crown outside of Boston. Twelve colonies formed a Continental Congress to coordinate their resistance, and established committees, British attempts to seize the munitions of Massachusetts colonists in April led to the first open combat between Crown forces and Massachusetts militia, the Battles of Lexington and Concord.

Militia forces proceeded to besiege the British forces in Boston, forcing them to evacuate the city in March, the Continental Congress appointed George Washington to take command of the militia.

Concurrent to the Boston campaign, an American attempt to invade Quebec, on July 2,, the Continental Congress formally voted for independence, issuing its Declaration on July 4. Sir William Howe began a British counterattack, focussing on recapturing New York City, Howe outmaneuvered and defeated Washington, leaving American confidence at a low ebb.

Washington captured a Hessian force at Trenton and drove the British out of New Jersey, in the British sent a new army under John Burgoyne to move south from Canada and to isolate the New England colonies.

However, instead of assisting Burgoyne, Howe took his army on a campaign against the revolutionary capital of Philadelphia. Burgoyne outran his supplies, was surrounded and surrendered at Saratoga in October, the British defeat in the Saratoga Campaign had drastic consequences.

British strategy depended upon an uprising of large numbers of armed Loyalists, in Spain joined the war as an ally of France under the Pacte de Famille, intending to capture Gibraltar and British colonies in the Caribbean.

Britain declared war on the Dutch Republic in December, in, after the British and their allies had suffered two decisive defeats at Kings Mountain and Cowpens, Cornwallis retreated to Virginia, intending on evacuation.

A decisive French naval victory in September deprived the British of an escape route, a joint Franco-American army led by Count Rochambeau and Washington, laid siege to the British forces at Yorktown.

With no sign of relief and the situation untenable, Cornwallis surrendered in October, Whigs in Britain had long opposed the pro-war Tory majority in Parliament, but the defeat at Yorktown gave the Whigs the upper hand.

United States — Forty-eight of the fifty states and the federal district are contiguous and located in North America between Canada and Mexico. The state of Alaska is in the northwest corner of North America, bordered by Canada to the east, the state of Hawaii is an archipelago in the mid-Pacific Ocean.

It is one of the worlds most ethnically diverse and multicultural nations, paleo-Indians migrated from Asia to the North American mainland at least 15, years ago. European colonization began in the 16th century, the United States emerged from 13 British colonies along the East Coast.

On July 4,, during the course of the American Revolutionary War, the war ended in with recognition of the independence of the United States by Great Britain, representing the first successful war of independence against a European power.

The current constitution was adopted in, after the Articles of Confederation, the first ten amendments, collectively named the Bill of Rights, were ratified in and designed to guarantee many fundamental civil liberties.

During the second half of the 19th century, the American Civil War led to the end of slavery in the country. By the end of century, the United States extended into the Pacific Ocean.

The end of the Cold War and the dissolution of the Soviet Union in left the United States as the sole superpower. It ranks highly in several measures of performance, including average wage, human development, per capita GDP.

The Congress meets in the Capitol in Washington, D. C, both senators and representatives are chosen through direct election, though vacancies in the Senate may be filled by a gubernatorial appointment.

Members are usually affiliated to the Republican Party or to the Democratic Party, Congress has voting members, Representatives and Senators. The House of Representatives has six non-voting members in addition to its voting members and these members can, however, sit on congressional committees and introduce legislation.

Puerto Rico, American Samoa, Guam, the Northern Mariana Islands, the members of the House of Representatives serve two-year terms representing the people of a single constituency, known as a district.

Congressional districts are apportioned to states by using the United States Census results. Each state, regardless of population or size, has two senators, currently, there are senators representing the 50 states.

Each senator is elected at-large in their state for a term, with terms staggered. The House and Senate are equal partners in the legislative process—legislation cannot be enacted without the consent of both chambers, however, the Constitution grants each chamber some unique powers.

The Senate ratifies treaties and approves presidential appointments while the House initiates revenue-raising bills, the House initiates impeachment cases, while the Senate decides impeachment cases.

A two-thirds vote of the Senate is required before a person can be forcibly removed from office. The term Congress can also refer to a meeting of the legislature.

A Congress covers two years, the current one, the th Congress, began on January 3,, the Congress starts and ends on the third day of January of every odd-numbered year. Members of the Senate are referred to as senators, members of the House of Representatives are referred to as representatives, congressmen, or congresswomen.

One analyst argues that it is not a solely reactive institution but has played a role in shaping government policy and is extraordinarily sensitive to public pressure. Several academics described Congress, Congress reflects us in all our strengths, Congress is the governments most representative body.

Congress is essentially charged with reconciling our many points of view on the public policy issues of the day. Residence Act — The federal government was located in New York City at the time the bill was passed and had previously been located in Philadelphia, Annapolis, and several other locations.

Congress passed the Residence Act as part of a compromise brokered between James Madison, Thomas Jefferson, and Alexander Hamilton, Madison and Jefferson favored a southerly site for the capital on the Potomac River, but they lacked a majority to pass the measure through Congress.

Meanwhile, Hamilton was pushing for Congress to pass the Assumption Bill, with the compromise, Hamilton was able to muster support from the New York State delegates for the Potomac site, while four delegates switched from opposition to support for the Assumption Bill.

In the meantime, Philadelphia was chosen as a temporary capital, Washington had authority to appoint three commissioners and oversee the construction of Federal buildings in the District, something to which he gave much personal attention.

On account of British military actions, the Continental Congress was forced to relocate to Baltimore, Lancaster, Pennsylvania, Congress requested that John Dickinson, the governor of Pennsylvania, call up the militia to defend Congress from attacks by the protesters.

In what became known as the Pennsylvania Mutiny of, Dickinson sympathized with the protesters, as a result, Congress was forced to flee to Princeton, New Jersey on June 21,, and met in Annapolis and Trenton, before ending up in New York City.

The United States Congress was established upon ratification of the United States Constitution in, the question of where to establish the capital was raised in The Southern states refused to accept a capital in the North, another suggestion was for there to be two capitals, one in the North and one in the South.

Congress approved a plan in for a capital on the Potomac, near Georgetown, in Maryland, and another capital on the Delaware River, this plan was rescinded the following year.

Establishing the capital was put on hold for years, until the Constitutional Convention was held in The Constitution said nothing about where the district would be. The debate heated up in when Congress convened for the first time under the Constitution, two sites were favored by members of Congress, one site on the Potomac River near Georgetown, and another site on the Susquehanna River near Wrights Ferry.

The Susquehanna River site was approved by the House in September, while the Senate bill specified a site on the Delaware River near Germantown, Congress did not reach an agreement at the time. The selection of a location for the capital resurfaced in the summer of, at the same time, Secretary of the Treasury Alexander Hamilton was pushing for Congress to pass a financial plan.

A key provision of Hamiltons plan involved the Federal government assuming states debts incurred during the American Revolutionary War, northern states had accumulated a huge amount of debt during the war, amounting to The Southern states, whose citizens would effectively be forced to pay a portion of debt if the Federal Government assumed it.

As the first Secretary of the Treasury, Hamilton was the author of the economic policies of the George Washington administration. He took the lead in the funding of the debts by the Federal government, as well as the establishment of a national bank, a system of tariffs.

His vision included a central government led by a vigorous executive branch. This was challenged by Virginia agrarians Thomas Jefferson and James Madison who formed a rival party and they favored strong states based in rural America and protected by state militias as opposed to a strong national army and navy.

They denounced Hamilton as too friendly toward Britain and toward monarchy in general, Hamilton was born out of wedlock in Charlestown, to a married mother of British and French Huguenot ancestry and a Scottish father.

His father, James A. Hamilton, was the son of laird Alexander Hamilton of Grange. Orphaned as a child by his mothers death and his fathers abandonment, Hamilton was taken in by an older cousin and he was recognized for his intelligence and talent, and sponsored by a group of wealthy local men to travel to New York City to pursue his education.

Hamilton attended Kings College, choosing to stay in the Thirteen Colonies to seek his fortune, discontinuing his studies before graduating when the college closed its doors during British occupation of the city, Hamilton played a major role in the American Revolutionary War.

At the start of the war in, he joined a militia company, in early, he raised a provincial artillery company, to which he was appointed captain. He soon became the aide to General Washington, the American forces commander-in-chief.

Hamilton was dispatched by Washington on numerous missions to convey plans to his generals, after the war, Hamilton was elected as a representative to the Congress of the Confederation from New York.

He resigned to practice law, and founded the Bank of New York, Hamilton was among those dissatisfied with the weak national government. He led the Annapolis Convention, which successfully influenced Congress to issue a call for the Philadelphia Convention in order to create a new constitution, Hamilton became the leading cabinet member in the new government under President Washington.

These programs were funded primarily by a tariff on imports, to overcome localism, Hamilton mobilized a nationwide network of friends of the government, especially bankers and businessmen, which became the Federalist Party.

A major issue in the emergence of the American two-party system was the Jay Treaty and it established friendly trade relations with Britain, to the chagrin of France and the supporters of the French Revolution.

Hamilton played a role in the Federalist party, which dominated national. In, he returned to the practice of law in New York and he tried to control the policies of President Adams. Thomas Jefferson — Thomas Jefferson was an American Founding Father who was the principal author of the Declaration of Independence and later served as the third President of the United States from to Previously, he was elected the second Vice President of the United States, Jefferson was primarily of English ancestry, born and educated in colonial Virginia.

Jefferson and James Madison organized the Democratic-Republican Party to oppose the Federalist Party during the formation of the First Party System, as President, Jefferson pursued the nations shipping and trade interests against Barbary pirates and aggressive British trade policies.

He also organized the Louisiana Purchase, almost doubling the countrys territory, as a result of peace negotiations with France, his administration reduced military forces.

Jeffersons second term was beset with difficulties at home, including the trial of former Vice President Aaron Burr, American foreign trade was diminished when Jefferson implemented the Embargo Act of, responding to British threats to U.

In, Jefferson began a process of Indian tribe removal to the newly organized Louisiana Territory. Jefferson mastered many disciplines, which ranged from surveying and mathematics to horticulture and he was a proven architect in the classical tradition.

Jeffersons keen interest in religion and philosophy earned him the presidency of the American Philosophical Society and he shunned organized religion, but was influenced by both Christianity and deism.

He was well versed in linguistics and spoke several languages and he founded the University of Virginia after retiring from public office. He was a letter writer and corresponded with many prominent and important people throughout his adult life.

His only full-length book is Notes on the State of Virginia, Jefferson owned several plantations which were worked by hundreds of slaves. Most historians now believe that, after the death of his wife in, he had a relationship with his slave Sally Hemings and fathered at least one of her children.

Various modern scholars are more critical of Jeffersons private life, pointing out the discrepancy between his ownership of slaves and his political principles, for example. Presidential scholars, however, consistently rank Jefferson among the greatest presidents, Thomas Jefferson was born on April 13,, at the family home in Shadwell in the Colony of Virginia, the third of ten children.

He was of English and possibly Welsh descent and was born a British subject and his father Peter Jefferson was a planter and surveyor who died when Jefferson was fourteen, his mother was Jane Randolph.

Peter Jefferson moved his family to Tuckahoe Plantation in upon the death of a friend who had named him guardian of his children, the Jeffersons returned to Shadwell in, where Peter died in, his estate was divided between his sons Thomas and Randolph.

Thomas inherited approximately 5, acres of land, including Monticello and he assumed full authority over his property at age The river is approximately miles long, with an area of about 14, square miles.

In terms of area, this makes the Potomac River the fourth largest river along the Atlantic coast of the United States, over 5 million people live within the Potomac watershed. The river forms part of the borders between Maryland and Washington, D.

The majority of the lower Potomac River is part of the State of Maryland, exceptions include a small tidal portion within the District of Columbia, and the border with Virginia being delineated from point to point.

Except for a portion of its headwaters in West Virginia. The largest flow recorded on the Potomac at Washington, D. The estuary also widens, reaching 11 statute miles wide at its mouth, Potomac is a European spelling of Patowmeck, the Algonquian name of a Native American village, perhaps meaning something brought.

Native Americans had different names for different parts of the river, calling the river above Great Falls Cohongarooton, meaning honking geese and Patawomke below the fall, meaning river of swans.

The spelling of the name has many forms over the years from Patawomeke to Patawomeck, Patowmack. The rivers name was decided upon as Potomac by the Board on Geographic Names in The river itself is at least two years old, likely extending back ten to twenty million years before present when the Atlantic Ocean lowered and exposed coastal sediments along the fall line.

The name Anacostia derives from the early history as Nacotchtank. Heavy pollution in the Anacostia and weak investment and development along its banks have led to it becoming what many have called D.

Maryland and federal governments have made joint efforts to reduce its pollution levels in order to protect the ecologically valuable Anacostia watershed, the mainstem of the Anacostia is formed by the confluence of the Northwest Branch and the Northeast Branch just north of Bladensburg, Maryland.

The watershed of the river roughly covers sq mi in eastern Montgomery County and northern Prince Georges County, as well as parts of Washington, on earlier maps, the river was known as the Eastern Branch of the Potomac River until it received its current, official name.

The Washington City Canal operated from until the mids, initially connecting the Anacostia to Tiber Creek and the Potomac River, the city canal fell into disuse in the late 19th century, and the city government covered over or filled in various sections.

One of the biggest problems facing the Anacostia River is raw sewage that enters the river, the sewage creates a public health threat because of fecal coliform bacteria and other pathogens, it also impairs water quality and can create hypoxic conditions that lead to large fish kills.

C, water and Sewer Authority in for allowing more than 2,,, US gallons of combined sewage and urban runoff to flow into the river via its antiquated combined sewer overflow system. In late, AWS and other organizations announced plans to sue the Washington Suburban Sanitary Commission over similar problems with contamination from the Maryland suburbs.

Another large source of pollution is the Washington Navy Yard. In its first year of operation, it removed more than pounds of litter per month from the river.

Conococheague Creek — Conococheague Creek, a tributary of the Potomac River, is a free-flowing stream that originates in Pennsylvania and empties into the Potomac River near Williamsport, Maryland.

It is 80 miles in length, with 57 miles in Pennsylvania and 23 miles in Maryland, the watershed of Conococheague Creek has an area of approximately square miles, out of which only 65 square miles are in Maryland.

The creek flows southwest, turning west at Caledonia State Park, the creek from Fayetteville to its confluence with Back Creek near Williamson is very polluted from farm runoff. This in turn has made parts of the lower East Branch ideal for catching huge crayfish at night, however, the West Branch flows for The West Branch is the pure of the two, owing mostly to the fact that a large portion of it runs through wilderness, making for very fine smallmouth bass, warmouth.

However, there are a few small sewage treatment plants on the lower West Branch, starting at Fort Loudon, northern pike and pickerel have been caught in the creek. It was listed on the National Register of Historic Places in, the crossing is where Braddocks forces crossed the Potomac after leaving Frederick on their way to Winchester.

It is the county seat of Washington County, and the largest city in a known as Western Maryland. The population of Hagerstown city proper at the census was 39,, Hagerstown ranks as Marylands sixth largest incorporated city.

Hagerstown has a distinct topography, formed by stone ridges running from northeast to southwest through the center of town and these ridges consist of upper Stonehenge limestone.

Many of the buildings were built from this stone, which is easily quarried and dressed onsite. It whitens in weathering and the conglomerate and wavy laminae become distinctly visible, giving a handsome.

Brick and concrete eventually displaced this native stone in the construction process, the population of the metropolitan area in was, Greater Hagerstown is the metropolitan area in the state of Maryland.

Despite its semi-rural Western Maryland setting, Hagerstown is a center of transit, interstates 81 and 70, CSX, Norfolk Southern, and the Winchester and Western railroads, and Hagerstown Regional Airport form an extensive transportation network for the city.

Hagerstown has often referred to as, and is nicknamed. A person born in Hagerstown is officially called a Hagerstonian, in, Hager officially founded the town of Elizabethtown which he named after his wife, Elizabeth Kershner.

In government forces arrested citizens during a riot which was staged by protesters in response to the Whiskey Rebellion. Hagerstowns strategic location at the border between the North and the South made the city a primary staging area and supply center for four major campaigns during the Civil War, in, General Robert Pattersons troops used Hagerstown as a base to attack Virginia troops in the Shenandoah Valley.

In, the city was the site of military incursions. In, Hagerstown was invaded by the Confederate army under Lt. John McCausland, into Hagerstown. The spread of smallpox by returning soldiers to families and friends was a problem during the war.

Founded in in the Province of Maryland, the port of Georgetown predated the establishment of the federal district, Georgetown remained a separate municipality until, when the United States Congress created a new consolidated government for the whole District of Columbia.

A separate act passed in specifically repealed Georgetowns remaining local ordinances, Georgetown is home to the main campus of Georgetown University and numerous other landmarks, such as the Volta Bureau and the Old Stone House, the oldest unchanged building in Washington.

The embassies of Cameroon, France, Kosovo, Iceland, Liechtenstein, Mongolia, Sweden, Thailand, Ukraine, situated on the fall line, Georgetown was the farthest point upstream that oceangoing boats could navigate the Potomac River.

In, English fur trader Henry Fleet documented a Native American village of the Nacotchtank people called Tohoga on the site of present-day Georgetown, the area was then part of the Province of Maryland, an English colony.

George Gordon constructed a tobacco inspection house along the Potomac in approximately, the site was already a tobacco trading post when the inspection house was built.

Warehouses, wharves, and other buildings were constructed around the inspection house. It did not take long before Georgetown grew into a port, facilitating trade.

In, the legislature of the Province of Maryland authorized the purchase of 60 acres of land from Gordon, a survey of the town was completed in February The Maryland Legislature formally issued a charter and incorporated the town in, robert Peter, an early area merchant in the tobacco trade, became Georgetowns first mayor in In, the Trinity Catholic Church was built, along with a parish school-house, construction of St.

Johns Episcopal Church began in, but paused for financial reasons until, and the church was finally consecrated in Fulton began publishing the Potomac Advocate, which was started by Thomas Turner.

Other newspapers in Georgetown included the Georgetown Courier and the Federal Republican, magruder, the first postmaster, was appointed on February 16,, and in, a custom house was established on Water Street.

Lingan served as the first collector of the port, in the s, City Tavern, the Union Tavern, and the Columbian Inn opened and were popular throughout the 19th century. Of these taverns, only the City Tavern remains today, as a social club located near the corner of Wisconsin Avenue.

As of the census, the population was, and it is the most populous county in Maryland. The county seat and largest municipality is Rockville, although the place of Germantown is the most populous place.

In, it was ranked by Forbes as the 10th richest in the United States, the Maryland state legislature named Montgomery County after Richard Montgomery, the county was created from lands that had at one point or another been part of Frederick County.

The countys motto, adopted in, is Gardez Bien, the countys motto is also the motto of its namesakes family. Before European immigration, the now known as Montgomery County was covered in a vast swath of forest crossed by the creeks and small streams that feed the Potomac.

A few small villages of the Piscataway, members of the Algonquian people, were scattered across the southern portions of the county. Captain John Smith of the English settlement at Jamestown was probably the first European to explore the area, during his travels along the Potomac River and throughout the Chesapeake region.

These lands were claimed by Europeans for the first time when George Calvert and he and other early claimants had no intention of settling their families. They were little more than speculators, securing grants from the colonial leadership, thus, it was not until approximately that the first British settlers began building farms and plantations in the area.

Most of these settlers were small farmers, growing wheat. Many of the farmers owned slaves and they transported the tobacco they grew to market through the Potomac River port of Georgetown. Sparsely settled, the farms and taverns were nonetheless of strategic importance as access to the interior.

General Edward Braddocks army traveled through the county on the way to its disastrous defeat at Fort Duquesne during the French, like other regions of the American colonies, the region that is now Montgomery County saw protests against British taxation in the years before the American Revolution.

In, local residents met at Hungerfords Tavern and agreed to break off commerce with Great Britain, following the signing of the Declaration of Independence, representatives of the area helped to draft the new state constitution and began to build a Maryland free of proprietary control.

The leaders of the new county chose as their county seat an area adjacent to Hungerfords Tavern near the center of the county, the newly formed Montgomery County supplied arms, food and forage for the Continental Army during the Revolution, in addition to soldiers.

Maryland — The states largest city is Baltimore, and its capital is Annapolis. George Calvert was the first Lord of Baltimore and the first English proprietor of the colonial grant. Maryland was the state to ratify the United States Constitution.

Maryland is one of the smallest U. It is the 42nd largest and 9th smallest state and is closest in size to the state of Hawaii, the next largest state, its neighbor West Virginia, is almost twice the size of Maryland.

Maryland possesses a variety of topography within its borders, contributing to its nickname America in Miniature. The mid-portion of this border is interrupted by Washington, D.

This land was ceded to the United States Federal Government in to form the District of Columbia, the Chesapeake Bay nearly bisects the state and the counties east of the bay are known collectively as the Eastern Shore.

Close to the town of Hancock, in western Maryland, about two-thirds of the way across the state. This geographical curiosity makes Maryland the narrowest state, bordered by the Mason—Dixon line to the north, portions of Maryland are included in various official and unofficial geographic regions.

The lack of any glacial history accounts for the scarcity of Marylands natural lakes, laurel Oxbow Lake is an over one-hundred-year-old acre natural lake two miles north of Maryland City and adjacent to Russett.

Chews Lake is a natural lake two miles south-southeast of Upper Marlboro. There are numerous lakes, the largest of them being the Deep Creek Lake. Maryland has shale formations containing natural gas, where fracking is theoretically possible, as is typical of states on the East Coast, Marylands plant life is abundant and healthy.

Middle Atlantic coastal forests, typical of the southeastern Atlantic coastal plain, grow around Chesapeake Bay, moving west, a mixture of Northeastern coastal forests and Southeastern mixed forests cover the central part of the state.

It is coterminous with the U. Census Bureau-census-designated place of Arlington, as a result, the county is often referred to in the region simply as Arlington or Arlington, Virginia.

In, the population was estimated at, The land that became Arlington was originally donated by Virginia to the United States government to form part of the new federal district of Columbia.

In, Congress returned the land southwest of the Potomac River donated by Virginia due to issues involving Congressional representation, the General Assembly of Virginia changed the countys name to Arlington in to avoid confusion with the adjacent City of Alexandria.

The county is situated in Northern Virginia on the bank of the Potomac River directly across from Washington. Arlington is also bordered by Fairfax County and City of Falls Church to the northwest, west and southwest, as of the census, the population was, Due to the proximity to downtown Washington, D.

It is also home to Ronald Reagan Washington National Airport, the many federal agencies, government contractors, and service industries contribute to Arlingtons stable economy. It is the county in the United States by median family income.

According to a study by Bankrate. Land grants from the British monarch were awarded to prominent Englishmen in exchange for political favors, one of the grantees was Thomas Fairfax, 6th Lord Fairfax of Cameron, who lends his name to both Fairfax County and the City of Fairfax.

With the passage of the Residence Act in, Congress approved a new permanent capital to be located on the Potomac River, the Residence Act originally only allowed the President to select a location within Maryland as far east as what is now the Anacostia River.

However, President Washington shifted the federal territorys borders to the southeast in order to include the city of Alexandria at the Districts southern tip. In, Congress amended the Residence Act to approve the new site, however, this amendment to the Residence Act specifically prohibited the erection of the public buildings otherwise than on the Maryland side of the River Potomac.

As permitted by the U. Constitution, the shape of the federal district was a square, measuring 10 miles on each side. As of the census, the population was 1,,, in, it was estimated at 1,,, making it the Commonwealths most populous jurisdiction, with The nature of population growth and methods of its estimation were furthered by Benjamin Gompertz and the logistic growth model by Pierre Verhultz, The latter was further developed by Raymond Pearl and Lowell Read This model was later re-stated in a more complete manner by Lois Dublin and Alfred Lotka John Snow might have been the precursor of the use of geographic information systems GIS through the mapping of victims of cholera to identify the source of the cause of their death.

In addition to the analysis of fertility and mortality, the analysis of migration the other variable in population change was also examined and Henry Carey put forward the migration gravity model — that was pursued by Ernst Ravenstein in his laws of migration This progression of demographic analysis led to the development of models that project populations in the future.

The cohort-component method of population projections was used by Edwin Cannan to project the population of England and Wales This involved the harnessing of efforts of many experts and the development of useful manuals.

One outcome was the preparation of worldwide population statistics that showed both strengths and gaps in demographic statistics in different countries. The United Nations also provided technical support to developing countries to improve their capacity for the collection and analysis of demographic information.

Indirect methods of the estimation of population and vital events were further developed to overcome the paucity of traditional tools such as censuses and vital events registration.

Ansley Coale and William Brass, and many others developed indirect methods of estimation of population and vital events. Analysis of demographic phenomena continues to be given attention. The observation that countries experience different mortality and fertility levels mooted by Warren Thompson in was developed into the concept of the demographic transition by Kingsley Davis in that helped to understand the pending population explosion in the following five decades.

Better insights into the factors underlying fertility levels were provided by the work of Kingsley Davis and Judith Blake This was extended by John Bongaarts and Robert Potter who devised a framework of the proximate determinants of fertility Economic models of family formation and fertility were explored by Gary Becker This inspirational work over the ages has provided current generations with the powerful tools of demographic analysis presented in the following chapters of this book.

References 5 References Pollard, A. Demographic techniques 4th ed. Dictionnaire de demographie [The dictionary of demography]. English version edited by C. A demography time line.

Department of Economic and Social Affairs. Chapter 2 Demographic Information 2. It examines the range of information involved and some of their relationships.

It reviews some basic demographic concepts and definitions. Further, it describes the major sources and collection methods of demographic data, including censuses, sample surveys, vital statistics registration, population registers, and administrative records.

In this context, it is connected with the measurement of births, deaths, migration and other vital events that have direct impact on population changes and in turn are affected by the size and composition of populations such as age distribution.

Demography also studies other population characteristics such as sex, marital status, living arrangements and household composition, language spoken, ethnic background, health and disability, education and training, employment status and occupation, income and household consumption, population densities and urban and rural residence.

Demographic studies often deal with the assessment of current characteristics like the number of people in a given area and their age and sex characteristics or trends over time such as population growth and changes in fertility and life expectancy.

Some other concerns in demographic analysis are the relationships between population composition such as age and vital events, for example, births or F. Sex could be defined as the biological characteristics of males and females — an ascribed characteristic.

Male and female gender attributes could be seen as psychological and social characteristics arising from belief systems of what male and female behaviour is or should be — an achieved characteristic.

Age Age is generally expressed in terms of time units after birth. The most common measure is the number of years after birth. The last birthday is usually the reference point to count the number of years after birth.

Other age related classifications may refer to stages of the life cycle. An infant is generally considered to be a person less than 1 year of age. The infant neonatal period has been defined as the first 28 days after birth.

There is more than one definition of the term child. Usually children are people less than 15 years of age. However, child mortality usually refers to deaths of children under 5 years of age. On the other end of the age range, old people are habitually defined as those who are 65 years of age and over.

The term adult can also have more than one definition. It is often associated with legal responsibility that varies from country to country. It could also be seen as people who are not classified as children that is those 15 years of age and over.

There is a degree of ambiguity involved and the term adolescent is frequently used to describe people in the age range of about 13—19 years of age. The varying perceptions lead to the need to have clear definitions in demographic analysis.

Births, Fertility and Fecundity In demographic analysis it is useful to distinguish between fecundity and fertility. Fecundity refers to the potential or capacity to reproduce.

The female reproductive period is from menarche to menopause, generally from the age of about 12—49 years. Fertility is defined in terms of the actual number of births that females have during their reproductive period.

A related term is pregnancy. It is the state of a female who has developed an embryo or a foetus in her abdominal area after the union of a spermatozoon and an ovum. Delivery is the result of a pregnancy of one 2.

Confinement is a pregnancy that leads in at least one live birth Australia b. Parity is the order of live births a woman has had. Accordingly, zero parity means that the woman has had no previous live birth, first parity means the first live birth a woman has had and second parity as the second.

If in her pregnancy the woman has a set of twins born alive, and these are her first live births, then the first twin born will be the first parity and the second born the second parity Canada Replacement fertility is the number of live births required for a couple to replace themselves.

This is estimated at 2. A birth is the result of a pregnancy that involves the complete expulsion or extraction of the product of a pregnancy regardless of the duration of pregnancy. It may result in live or stillborn births and single or multiple births.

A live birth is a birth that after separation breathes or shows any evidence of life, such as beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles, whether or not the umbilical cord has been cut or the placenta is attached Canada Stillbirth foetal death is the death of the product of a pregnancy prior to complete expulsion or extraction and is indicated by the fact that after such separation the foetus does not breathe or show any evidence of life, such as the beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles.

Registration of foetal deaths may take place if they have the birth weight of g or more or the duration of the pregnancy is 20 weeks or longer Canada The term nuptial birth may be applied to a child born to parents who are legally married.

Also related to marital status is a paternity acknowledged birth. This is an ex-nuptial birth where the father acknowledges paternity Australia b. Births and other vital events may be counted either by year of registration, the date when they were registered, or year of occurrence when the event actually took place.

Similarly, births and other vital events can be counted at their place of occurrence de facto or at the place of residence of the person experiencing the vital event in question de jure.

Deaths, Mortality and Life Expectancy Mortality is concerned with deaths in a given population. A death is the complete and permanent disappearance of all evidence of life after a live birth has taken place.

It excludes deaths before a live birth Australia c. However, as will be seen, stillbirths are included in the measurement of perinatal stillbirths and neonatal deaths rates.

Mortality measures the number of deaths over a period of time, usually 1 year, and relates it to the reference population. The importance of deaths early in life has led to the classification of deaths to include perinatal, neonatal and infant deaths.

Perinatal deaths are the number of deaths of stillbirths foetal deaths of at least 20 weeks or g birth weight plus neonatal deaths. Neonatal deaths are defined as the number of deaths of live born infants within 28 days of birth, and infant deaths are the number of deaths of all live births before 1 year of age 10 2 Demographic Information Australia Perinatal death rates relate perinatal deaths to the number of stillbirths plus the number of live births, while neonatal and infant mortality rates relate these deaths to the number of live births.

Mortality also relates deaths to age and other characteristics of the relevant population. A linked measure is survival or life expectancy in terms of the average number of years that people in a given population are likely to live.

This may be estimated at birth or some other age. Death may affect the status of surviving relatives. Orphans are children with at least one parent dead. Widowed is the status of a male or female whose partner has died.

The classification of causes of death is another dimension of the analysis of mortality. Causes of death may be underlying and multiple, with main and possibly secondary causes. Accidental and violent causes may be classified according to the external cause rather than the nature of the death.

Migration Migration refers to the movement of people from one location to another. Migration out of an area is known as emigration and that into an area is immigration. Net migration is the difference between emigration and immigration.

It can be positive or negative depending on the relative sizes of the two flows. Migration may be temporary or permanent depending on its intended purpose and or period of time involved.

Different countries may apply different definitions. Migration may take place within a country and be denoted as internal domestic migration or international across country borders. It is concerned with the origin and destination of the individuals who move.

In addition to the count of migration flows, demographic analysis is also concerned with relating these flows to the reference population at origin and destination. Marital Status Marriage is the union of two or more people who cohabit and form a family.

Marriage may be registered according to local legal statues. Marriage may be of a male and a female, or of more than two people. Marital legal status is evolving and marriage of people of the same sex may be legal and registered.

De facto or social marital unions may also take place and may or may not have legal status. It may be said that a marriage exists when two people live together as husband and wife, or partners, regardless of whether the marriage is formalised through registration Australia a.

The following classification tends to be applied: A household is a group of two or more people who live in the same dwelling. A dwelling is a place where people live. It may be a house, an apartment or some other living place such as a caravan in a park.

These dwellings may be private or non-private and may be occupied or not occupied. People in households may be unrelated or related but share their food and other basic living essentials.

There are also single person households who live by themselves in a dwelling and make their own arrangements for basic living essentials including food. Households may be of one-person, group of unrelated people, same-sex couple, and group of related people either by couple union or blood.

A family is a household of two or more people who are related by union bonds, such as a couple, or some blood relationship such as a child-parent relationship.

Families include couples only, couples with dependent children, single-parent with dependent children, and extended families that may include other relatives related by union or blood.

Usually, people who live in non-private dwellings such as hostels and boarding houses, hotels, hospitals and other institutions are not counted as members of households Australia Applied demography is concerned with the application of demographic perspectives and approaches to the identification and management of social, government and business problems.

Usually, censuses are carried out on a country wide basis at a given date or period of time. According to the United Nations, censuses should have the following attributes: It requires the definition of the territory to be covered and parts thereof and reasonable access to people.

In view of these requirements, censuses should take place at a time when people are easily contacted in their usual place of residence. Accordingly, the timing of the census should avoid times of the year when weather may make communications difficult or when people may be away from their usual residence, as in case of seasonal work away from home or holidays.

The substantial resources involved tend to limit the periodicity of census to every 5 years, such as in the case of Australia, or ten as in the United States and many other countries. The enumeration of individuals may follow different rules depending on residence status.

For instance, short-term visitors may not be taken into consideration; the same might apply to the representatives of foreign governments or international organizations living in the country.

The inverse might apply to members of the armed forces and Foreign Service personnel living in other countries. Further, residents may be classified according to their usual residence de jure or where they are at the times of the census de facto.

Censuses are major undertakings requiring planning and a large organization. Often, they are the largest data collection in any country. Censuses may follow a traditional approach of enumerating each individual within a given geographical area at a given day or may use different spatial and time approaches.

Frequently, population censuses are done in conjunction with housing censuses United Nations The extent of the information collected varies from country to country. For instance, the census in the United States collects some information from all households and additional information from a sample of households.

In addition to the count and the record of the place of residence, censuses may collect information on a range of individual characteristics. The most common are age and sex. However, information on marital status, level of education, labour force status, occupation, income, country of birth, religion and previous place of residence may also be collected Australia a.

Census may also be used to estimate both domestic and international migration by asking questions on the residence of individuals being enumerated at some past date such as the previous census.

The difficulties in carrying out the total enumeration of a given population tend to result in inaccuracies. There are two main kinds of errors: Therefore, validity tests tend to be carried out to improve accuracy.

These include the examination of age and sex distributions using information from previous censuses and existing knowledge of fertility, mortality and migration from vital statistics and other sources.

Postenumeration surveys of a representative sample of the population may also be used to test coverage and response errors in reporting of individual characteristics United Nations They are useful complements to demographic information obtained through censuses, and other sources.

The dated nature of censuses information also makes surveys useful tools in the compilation of demographic estimates between censuses. Surveys have a number of advantages. They tend to be less costly than censuses, can be designed with a specific purpose in mind and can dwell in depth into the subject matter.

Further, they can be used in combination with demographic data obtained from other sources. After censuses are carried out, post-enumeration surveys enable the estimation of the census coverage and reliability.

When surveys include all individuals in the target population they have the attributes of a census. Here, the concern is with surveys that use a sample of the target population to assess their characteristics.

There are two major types of sample surveys: In probability samples each individual in the target population has an equal chance of being selected and thus the probability of selection can be estimated numerically.

Non-probability samples take many different approaches and formats. Among them, convenience or accidental sampling is a non-random sample used because of ease of access to the individuals being sampled.

Some enquiries use university students, because they are conveniently available subjects. Quota sampling involves the non-random selection of individuals with different characteristics such as sex to ensure that they are represented in the sample.

This method may use a proportional approach in considering the adequacy of representation, for example, a sample in which half of the total number are males and the other half are females. Purposive or judgmental sampling involves another non-random selection of subjects.

The selection is based on the knowledge of those undertaking the survey of the types of individuals that should be included in the survey. Yet another kind of non-random sampling is snowball sampling.

It consists of the selection of some individuals of interest for the survey and then using their knowledge to reach others of interest for the survey. The approach tends to be used when there is difficulty in identifying individuals of interest to be surveyed.

The usefulness of non-probability sampling is limited because it may not be representative of the target population and the survey results may be biased. Therefore, it is uncertain whether findings can be generalised to the target population.

A more reliable approach is the use of probability sampling even though it might be more costly Dillman et al. Probability sampling allows the estimation of sampling errors which are used to decide the significance or otherwise of an estimate based on the sample for further information, see any standard textbook on Statistics.

There are a number of probability sample designs that are available. Only four designs that are commonly used are described below. In many surveys more than one sampling techniques may be used.

Each individual item has an equal chance of being selected and given equal value. This is the simplest of probability sampling techniques. For the systematic sampling, an inventory list of individuals or households or items or events is compiled or is available to constitute the sampling frame.

Then, say, every fifth or tenth individual or household on the list is selected for the sample. This is not strictly a random sample but is usually a reasonable practice, as long as there is no bias in the structure or order of the listing or some periodicity.

The multistage sampling usually involves the random selection of a higher order unit such as a region. From this, a second stage sampling may involve the random selection of households in that region.

In a third stage, individuals may be randomly selected from the households selected. The stratified sampling technique ensures sufficient representation in the sample of different groups in the population, the sample may be made up of strata according to the characteristics of different groups in the population.

This may result in a lower cost and more representative sample. The strata size may be in proportion to its proportion in the population, otherwise relative weights need to be given to each stratum in relation to its proportion in the population.

Cluster sampling may be used when the population to be sampled is bunched and each bunch or group is close to being representative of the population or having similar characteristics.

The clusters are randomly selected and every individual, or household, or item or event in the selected clusters may be included in the sample. In order to ensure representative findings, it is important that either the clusters are all of the same size or weights are assigned to overcome the difference in size of the different clusters.

Surveys can be concerned with a variety of demographic information such as fertility, health and disability status, labour force participation, training and occupation, income levels, wealth and poverty, nutrition and exercise, time use and household expenditure.

They may be ad hoc in nature or be undertaken periodically and allow for the assessment of change and trends over time. They may be concerned with the whole population or defined groups within it.

As is the case with a full census, the major trade-off in a sample survey is between precision, cost and time Swanson Sample surveys concerned with employment are carried out in most countries.

Their frequency allows the study of trends over time and seasonality. Their usefulness is often enhanced by piggybacking questions concerned with other subjects as in the case of the Australian Multi-Purpose Household Survey Australia Housing and household sample surveys can be particularly useful in countries that take a regular census.

For instance, the English Housing Survey —10 collected information on age, economic status, ethnicity and marital status and income of the household reference person. It also provided information on household size and composition, and type of housing tenure United Kingdom Household sample surveys are conducted frequently to assess household income and expenditure 2.

Yet, other sample surveys collect data on a range of human activities including how people use their time Australia They were followed by the Demographic and Health Surveys, again among many developing countries to gain information on fertility, mortality and health related issues Zuehike Other countries also conduct surveys with a focus on health status.

However, its degree of completion varies depending on the level of civil administration of a country and difficulties in reaching people in less accessible areas. Accordingly, some countries have to rely on sample surveys and other methods to gain a more complete view of fertility and mortality, especially in rural areas.

In some countries, registration data can be more a source of confusion than usefulness, as far as demographic information is concerned, and care needs to be taken in testing its coverage and reliability; while in others these data are most valuable.

Birth registration can present problems such as the distinction between live and stillbirths and related measures of birth and perinatal death rates Sect. This can lead to both the under-enumeration of live births and infant mortality.

Death registration generally records the age and sex of the individual, place of birth, marital status, occupation and cause of death. Records can suffer from various shortcomings.

The first is the question of completeness of coverage due to similar issues as those of birth registration. Further, details regarding age, marital status and occupation can also pose challenges due to definitions and memory lapses.

The cause of death is also an issue in terms of definitions. There can also be lack of coverage because, in some cases, deaths may take place without medical assessment of the cause of death.

The value of registration data on marriages and divorces, as a source of information on family relationships is changing considerably, as social values and partnerships evolve. Registration usually records de jure but not de facto relationships or separations.

De facto marital status has risen considerably in some countries. This 16 2 Demographic Information has led to some countries to offer legal status to cohabitation and even registration without legal marriage OECD Further, there may be differences in legal statutes concerning marriage and divorce within the same country and across countries.

Nevertheless, marriage registration continues to provide information on a dimension of social relationships: The recorded information usually includes the date of the event and of birth and sex of the partners, their usual residence, occupation and religion, as well as any previous legal marital status.

In addition, divorce may also include the information on any children involved. However, they can be useful sources of demographic data United Nations They provide for the systematic record of the identity and characteristics of each individual resident either in a country or an area within.

The data recorded may include the date of birth, sex, marital status, place of birth and nationality. In some cases, a unique number may be given to each individual on the register.

For a population register to supply reliable statistics it should have attributes such as: The accuracy and timeliness of the data in population registers can be affected when vital events and statistics are recorded by different agencies and the register is dependent on record linkage from more than one source.

In some instances, delay in the transmission of information from local area registers to central agencies can affect their accuracy Netherlands Yet, another issue is international and internal migration that may lead to duplication or omission due to differences in definitions to distinguish visitors from residents.

Concerns have also been raised about the confidentiality of a wide range of information about a single individual in a given source. Some approaches to data handling can reduce some of the risks involved.

Similar issues have been raised about confidentiality of census information. Some Scandinavian and other countries are compiling their censuses from their population registers and complement them with other sources.

For instance, Finland has established a Population Register Centre and uses an individual identity number. The Central Population Register began to function in In, the 2.

Population registers can also be used to estimate both international and internal migration. This primary function may pose problems in the collection of demographic data because of: However, they also found that some people registered in these programs had been missed by the census.

This implies that although administrative records may be, at times, of poor quality they may also contain useful information. An advantage in the use of administrative records is that most of the large costs involved in data collection have already been incurred.

The growing use of electronic data entry and classification has also improved retrieval of these data and their manipulation for statistical purposes. Greater demand for statistics, concern with data collection fatigue and sometimes budgetary constraints have contributed to efforts in the use of administrative records as a source of statistics Brackstone Administrative records collect a wide range of information at various levels from countrywide programs such as taxation and social security benefits to local government administrative concerns such as housing.

The registration of vital events has already been discussed as a source of demographic information Sect. Statistics from schools are a major source of information on enrolments and levels of education achieved.

Hospital statistics can contribute to the assessment of dimensions of health status. Administrative records of international arrivals and departures and the granting of visas are useful in the estimation of international migration.

Taxation statistics can also be used to assess levels of income and also about the movement of people from year to year. The same applies to data kept by public utilities such as electricity, gas and water services.

They may collect the data from primary sources through censuses and surveys or retrieve data from other agencies, individuals or corporations. Information may be made available in a variety of media and through several means.

These include publications, special tabulations, samples of individual records in electronic media or through the Internet. All of these publications provide demographic information on a periodic basis.

The World Bank produces a World Development Report and various regional agencies also compile and publish a range of demographic information. In addition to publications, most national and international agencies also provide demographic data on their websites through the Internet.

Links to some of the major organisations are given below: Concepts, sources and methods, Apr Australian Bureau of Statistics. How Australians use their time, Perinatal deaths, Australia Household and family projections, Australia, to Census dictionary Australia Issues in the use of administrative records for statistical purposes.

Survey Methodology, 13 1 , 29— The world fertility survey: An assessment of its contribution. Internet, mail, and mixed-mode surveys: The tailored design method.

Life table estimates for the Philippines, its regions and provinces, by sex: Use of registers and administrative data for statistical purposes: Best practices of Statistics Finland.

Annual report on the family income and expenditure survey Statistics on the causes of death, Malaysia Cohabitation rate and prevalence of other forms of partnership.

Organization for Economic Cooperation and Development. The World Fertility Survey: An international program of fertility research. Studies in Family Planning, 5 2 , 35— A manual for sociology students.

Department for Communities and Local Government. Principles and recommendations for population and housing censuses — revision 2 Statistical papers series M no. National health interview survey.

Centers for Disease Control and Prevention. International classification of diseases ICD. The demographic and health surveys at 25 years and beyond. Chapter 3 Some Basic Statistical Measures 3. The concepts are defined in general terms without going into theoretical details.

Methods of calculation of various measures are described. The statistical measures discussed in this chapter consist of counts, frequencies, proportions, rates, various measures of central tendency, dispersion, comparison, correlation and regression.

This is useful because the level of measurement helps the selection of what statistical analysis is most appropriate. Several classifications can be used. This book uses the four-fold classification system proposed by Stevens that classifies data as being 1 nominal, 2 ordinal, 3 interval and 4 ratio.

There are other systems such as the two-fold classification of 1 discrete and 2 continuous. In the classification system proposed by Stevens, the nominal level is known as the lowest level of measurement.

Here, the values just name the attribute uniquely and do not imply an ordering of cases. For example, the variable marital is inherently nominal. In a study it might be useful to have attributes such as never married, married, separated, divorced and widowed.

These attributes are mutually exclusive and exhaustive. In the latter, the numbers are not numbers in a real sense since they cannot be added or subtracted. Thus, numbers assigned to serve as values for nominal level variables such as marital status cannot be added, subtracted, multiplied or divided in a meaningful way.

An exception is the dummy coding of F. Dummy coding allows some limited functions to be performed. The next level of measurement is ordinal. Although it is at a higher level of measurement than the nominal category, it is still considered a low level of measurement.

The attributes are rank-ordered but the distances between the attributes are not fixed. For instance, in a questionnaire, people are asked if they think that population growth is a major world problem and five possible response categories are given: It can be seen that strongly agree coded as 5 indicates more agreement than a response coded as 4 somewhat agree, and so on.

However, the distance between the five categories is not fixed. It cannot be said whether the distance from strongly disagree 1 to somewhat disagree 2 is the same as that from strongly agree 5 to somewhat agree 4.

All it can be said is that codes 1 to 5 preserve the order of agreement. Coding ordinal levels with numbers is a grey area between the coding with numbers at nominal level for which there is no meaningful addition, subtraction, multiplication and division and interval level numbers that can be added and subtracted, and ratio level numbers for which there is meaningful addition, subtraction, multiplication and division.

In some situations, numbers at ordinal level can be treated as having an interval and in others they cannot. It depends on the coding assigned to the attributes of ordinal level variables.

The interval level is a much higher level of measurement than the nominal level and even higher than the ordinal level. At this level, the numbers of the distance between attributes that can be meaningfully added and subtracted.

This means that there is a fixed distance between the temperature levels — as when a ruler is used to measure the distance between two points using the same distance scale.

This means that numbers measured at the interval level cannot be multiplied or divided in a meaningful way. At the highest level of measurement is the ratio. A true zero exists for the numbers at this level.

This means that numbers can be multiplied and divided as well as added and subtracted in a meaningful way. For instance, in the Fahrenheit system for measuring temperature, zero is not the absence of heat.

Thus, measurement is at the interval level because the distance between points is fixed and on the same scale. However, in the Kelvin system for temperature measurement there is an absolute zero at which molecular action ceases.

This means that the Kelvin scale is at the ratio level of measurement. Variables at higher levels of measurement can be transformed into lower levels of measurement. This is the case with grouping the ratio level variable of income in Table 3.

Here the variable measured at ratio level was transformed into a variable measured at ordinal level. This process could be continued by classifying the income data into two groups labelled Yes and No, where these two categories would be those with income below or above a certain amount of income say the average income.

This transformation would re-code income data into a nominal level variable. The analysis of demographic information can be of a descriptive nature, as in the case of the estimation of percentages, measures of central tendency and dispersion discussed later.

It may also be of an inferential nature. In that case, demographic analysis is concerned with relationships either between groups in or characteristics of population, as in the case of correlation and regression, briefly discussed later.

Statistical methods should be consistent with the nature of the data, as categorical and ranked data may require different methods of analysis. For example, the estimated population of the world was 6, million people in mid United Nations This is just one count.

Other counts may relate to the population of different regions of the world, for example, that of Asia was 4, million and Europe million. On a smaller scale, counts may consist of data based on a few observations, such as the hypothetical data on daily income dollars of 30 people in Table 3.

The daily income of these 30 people can be summarised into income groups that cover the range of individual incomes. In making this conversion, data at the interval level is transformed into ordinal level data.

In this instance, each individual is classified according to their daily income and counted as a member of the relevant income group. The result is given in Table 3. However, the size of each income group could be different and there could be a smaller or larger number of income groups.

Nevertheless, the sum of all groups would continue to be Such a distribution is called a frequency distribution because it counts the number of observations frequency in each group.

Three features of each group need to be considered, when estimates are made from the frequency distribution: In fact, the upper limits are just less than 30, 50, 70, 90 and respectively.

As stated, in this example the width interval is the same for all, except the first, income groups but groups may have unequal intervals. The data presented in Table 3. In this example, the ungrouped data are measured at the ratio level while in their grouped form they are measured at the ordinal level.

This converted into a percentage is 0. Accordingly, the proportion of the world population living in Asia was 0. In other words, there were close to 60 people living in Asia out of every in the world.

Frequency distributions can be converted into proportional or percentage frequency distributions by dividing the frequency in each group by the total number, as illustrated in Table 3.

A hypothetical distribution of males and females by income group is shown in Table 3. Such a table is called a bivariate table as it involves two variables: It can also be called a five by two table since it crossclassifies five income values by two sex values.

In this case, income is at the ordinal level of measurement and sex is at the nominal level. There are three ways of calculating percentages from a bivariate table, as shown in Tables 3.

Percentages have been calculated separately for females and males in Table 3. The percentage total in each column is The last column has the percentage distribution of all persons according to income.

It is the same as that given in the fourth column of Table 3. The percentage distribution of males and females can also be estimated for each income group as in Table 3.

Each row adds to The last row in the table shows that Totals for columns may not add due to rounding Table 3. Totals for rows may not add due to rounding All persons Totals in columns and rows may not add due to rounding Each cell of Table 3.

Relative measures can also be 3. United Nations No. Relative measures are similar, but each has a distinct meaning. A ratio is simply a number divided by another. However, in demographic analysis a ratio is usually the quotient of two groups of people with different characteristics in the same population or the quotient of one variable by another.

As stated earlier, in there were 6, million people in the world; the number of males was 3, and females 3, million United Nations The ratio of males to females was: The number of births in China during was estimated as Accordingly, the rate of births in China during was: It relates a number of events or some other demographic variable to the average population during the specified period of time, usually the mid-period population.

In other words, a rate is the number of events or some other demographic variable occurring during a given period of time divided by the population at risk of the occurrence of those events or the population to which the demographic variable relates to.

For example, the birth rate is the number of births from a given population divided by the population exposed to the risk of having those births. Rates of births to population in Egypt and the United States are presented in Table 3.

Some rates may be expressed per person, in percentages, per thousand people or even per hundred thousand depending on the size of the number of events in relation to that of the relevant population.

Although the concept of a rate is clear, it is often difficult or practically impossible to get an exact measure of the population at risk to the occurrence of the particular event.

For instance, only females in their childbearing years are 28 3 Some Basic Statistical Measures Table 3. Some may die during the period — in a given area — some may move away and other move in.

How can the population exposed to the risk of giving birth in that area be defined and measured? This problem is usually solved by using the midyear year or period of time population as an approximation.

This solution is based on the assumption that births and deaths occur evenly throughout the year, so that the midyear population is a measure of the average of the reference population during the year.

The resulting rate is called a central rate. Usually, the use of the midyear population is adequate to get reasonable results. However, if the population is growing at a substantial rate throughout the year, it might be more adequate to use the average of the population at given intervals during the year.

A distinction can also be made between central rates and probabilities. In a central rate the denominator is the population at the mid-point of the time period say the middle of the year.

It is meant to represent the average population during the time period. In a probability, the denominator is the population at the beginning of the time period. This is thought to correspond more closely to the population at risk of the occurrence of an event during the time period.

The distinction between central rates and probabilities is somewhat fuzzy because of the movement of people into and out of an area. For example, if age-specific rates are considered, a true single-year probability can be calculated using the population of the area at the beginning of the year and the number of deaths that took place during the year to members of the population, at the beginning of the year, for each age cohort.

However, some deaths will be missed by the death registration system for the area because they relate to people who moved out of the area during the year. Further, some deaths will be improperly included because they refer to people who moved into the area during the year.

Consequently, it is difficult if not impossible to estimate true probabilities for a variety of demographic measures. The term rate is used loosely in demography, as it is elsewhere. Many measures called rates are really ratios.

A growth rate, for example, is a ratio of population change over a time period to the population at the beginning of the time period. The most commonly used are the arithmetic mean also referred to as the mean, median and mode.

The mean, median and mode can be used with variables measured at the interval or ratio levels, and some times at the ordinal level. If variables are measured at the ordinal or nominal level, the mode is generally the most meaningful measure of central tendency.

Two other less frequently estimated means are also discussed: As their names suggest, they were designed to use variables measured at the interval and ratio levels.

The estimated mean of the income data in Table 3. It is assumed that the individual incomes, or any other variable in the calculation of the mean, are evenly distributed within each group, and the mid-point in the group is taken as the average value of xi for the whole group.

An example of the computations involved in the estimation of the mean in grouped data Table 3. The mid-point xi is multiplied by the frequency for that group in column 2 , i.

If the width of the last group is open ended, that is, the upper limit is not specified, then the estimation of the mean will depend upon the assumption regarding the length of that interval.

For example, if in Table 3. The AM may be affected by extreme values. For instance, in a series of six numbers 23, 25, 30, , 20, and 24, the AM is 62, despite the fact that all but one values lie between 20 and The following measures of central tendency are not affected by extreme values to the same extent as the AM.

For a given set of numbers x1, x2,. The value of n may be any number from 2 onwards. An easier way to calculate the n th root is through logarithms. Two types of logarithms are: The former are referred to as logarithms log and the latter as natural logarithms LN or ln.

The LN of is 4. Antilogarithms enable the conversion of a logarithm back into the original number. The antilogarithm of log is 10x and that of LN is ex. Most calculators have log, 10x, LN or ln and ex keys.

The following rules apply to both log and LN: In general, the following relationship holds for any series of numbers: Usually, GM and HM are not calculated for grouped data. In other words, the median divides the ordered set into two equal parts: Accordingly, the first step in the estimation of the median for the figures in Table 3.

The median daily income is The p is 0. The median group is identified by halving the total frequency n. This is the first group that has a 3. The value of L is the lower limit of the median group, i is the width, and f is the frequency.

C is the cumulative frequency of the group preceding the median group and n is the total of the frequencies for all groups. Ungrouped data give more precise estimates of both AM and the median, but demographic data are generally available in grouped formats.

Depending on the nature of the analysis the median may be preferred to the AM. The median is often used in place of the mean when data are highly skewed that pulls the mean way from the bulk of the observations.

The median is not affected by the skewness of the distribution of observations. In grouped data, it is the group that has the largest frequency if the class intervals are about the same.

Some distributions have a single mode while others may have two or more modes. In this example, the mode is 30—34 years age group, as this has the largest number of births recorded.

It is an example of a distribution with one mode uni-modal distribution. Japan An example of a distribution with two modes bi-modal distribution is the number of Japanese females in the labour force by age Japan in Fig.

In this instance, there were two modes: There may be distributions with more than two modes. The value of the mode is that corresponding to the top of the hump. This is also the median that divides the distribution into two equal halves.

The AM of this distribution also coincides 3. This distribution rarely occurs in the real world. However, it is an important component of the theory that underlies statistical inference.

A non-symmetrical distribution is called a skewed distribution. There are two types of skewed distributions: In a positively skewed distribution the value of both the median and the mean AM are larger than the mode.

In a negatively skewed distribution they are both smaller than the mode Figs. The properties of these three types of distributions can be summarised as follows: These properties are used in developing measures of skewness.

The variance and the standard deviation can be estimated for data at the interval and ratio levels and sometimes for data at the ordinal level. They should not be used with data at the nominal level unless the data have been transformed using dummy coding.

Quantiles are essentially measures of data at interval and ratio levels that have been transformed into ordinal categories. The equations to calculate the variance VAR and the standard deviation SD for a set of n numbers x1, x2,.

These differences are squared multiplied by themselves column 3 to convert them into positive values. The standard deviation SD is the square root of the variance.

The standard deviation can be viewed as the average expected error that results from using the mean AM to predict individual values of the variable in question. For example, if AM of This is an important concept to remember because it forms a basis to evaluate a regression model, a topic that is discussed later on.

The denominator is sum of frequencies n minus 1. These two measures are Although the median is usually considered a measure of central tendency, the median is a quantile that divides a series into two equal parts.

In addition to the median, quartiles, quintiles and deciles are some of the other commonly used quantiles. They represent the partition of a series into four quartiles, five quintiles and ten deciles equal parts.

The number of positional points required is one less than the partitions, because the last positional point is the highest value of the series. Thus, there is no need to calculate the fourth quartile or the fifth quintile or the tenth decile as they are the last value of the ascending series.

Quantiles for Ungrouped Data The identification of the quantile points involves first the selection of the number of partitions required. The series in Table 3. The median that divides the series into two equal parts has already been shown as lying between The median is, by definition, equal to the second quartile Q2.

The lowest quartile point Q1 is positioned at Similarly the third quartile point Q3 divides the second half of the series into two equal parts and is located at The fourth quartile point Q4 is The five quintile points QN1—QN5 are as indicated above.

The ten decile points D1—D10 , are noted above. Quantiles for Grouped Data The estimation of quantiles in frequency distributions starts by the identification of the interval that contains the quantile group.

The procedure is essentially the same as that for the calculation of median described earlier. The first step involves the identification of the particular quantile group.

This depends on whether quartiles, quintiles or deciles are being calculated. It is the same as Eq. Income data from Table 3. Once a particular quantile group is identified the values of L, i, f, n and C are substituted in Eq.

The following examples are concerned with the estimation of the location values for the third quartile Q3 , the second quintile QN2 and the sixth decile D6 from Table 3.

Frequency fi 2 8 10 6 4 30 Cumulative frequency Ci 2 10 20 26 To estimate Q3, the corresponding value of p is 0. Multiplying this by n 30 equals The fourth column of Table 3. Substituting these values in Eq.

To estimate the second quintile QN2 , the value of p is 0. From the fourth column of Table 3. Substituting the above values in Eq. To estimate D6, the value of p from Table 3.

This value multiplied by n 30 equals The comparison of the values of the location points for various quantiles of the grouped and ungrouped data indicates that the estimated quantiles are similar.

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