Census, term usually referring to an official count by a national government of its country’s population. A population census determines the size of a country’s population and the characteristics of its people, such as their age, sex, ethnic background, marital status, and income. National governments also conduct other types of censuses, particularly of economic activity. An economic census collects information on the number and characteristics of farms, factories, mines, or businesses.
Most countries of the world conduct population censuses at regular intervals. By comparing the results of successive censuses, analysts can see whether the population is growing, stable, or declining, both in the country as a whole and in particular geographic regions. They can also identify general trends in the characteristics of the population. Because censuses aim to count the entire population of a country, they are very expensive and elaborate administrative operations and thus are conducted relatively infrequently. The United States conducts a population census every ten years (a decennial census), and Canada conducts one every five years (a quinquennial census). Economic censuses are generally conducted on a different schedule from the population census.
Censuses of population usually try to count everyone in the country as of a fixed date, often known as Census Day. Generally, governments collect the information by sending a questionnaire in the mail or a census taker to every household or residential address in the country. The recipients are instructed to complete the questionnaire and send it back to the government, which processes the answers. Trained interviewers visit households that do not respond to the questionnaire and individuals without mail service, such as the homeless or those living in remote areas.
|II||USES OF CENSUS INFORMATION|
Governments use census information in almost all aspects of public policy. In some countries, the population census is used to determine the number of representatives each area within the country is legally entitled to elect to the national legislature. The Constitution of the United States, for example, provides that seats in the House of Representatives should be apportioned to the states according to the number of their inhabitants. Each decade, Congress uses the population count to determine how many seats each state should have in the House and in the electoral college, the body that nominally elects the president and vice president of the United States. This process is known as reapportionment. States frequently use population census figures as a basis for allocating delegates to the state legislatures and for redrawing district boundaries for seats in the House, in state legislatures, and in local legislative districts. In Canada, census population data are similarly used to apportion seats among the provinces and territories in the House of Commons and to draw electoral districts.
Governments at all levels—such as cities, counties, provinces, and states—find population census information of great value in planning public services because the census tells how many people of each age live in different areas. These governments use census data to determine how many children an educational system must serve, to allocate funds for public buildings such as schools and libraries, and to plan public transportation systems. They can also determine the best locations for new roads, bridges, police departments, fire departments, and services for the elderly.
Besides governments, many others use census data. Private businesses analyze population and economic census data to determine where to locate new factories, shopping malls, or banks; to decide where to advertise particular products; or to compare their own production or sales against the rest of their industry. Community organizations use census information to develop social service programs and child-care centers. Censuses make a huge variety of general statistical information about society available to researchers, journalists, educators, and the general public.
|III||CONDUCTING A CENSUS|
Most nations create a permanent national statistical agency to take the census. In the United States, the Bureau of the Census (Census Bureau), an agency of the Department of Commerce, conducts the national population census and most economic censuses. In Canada, the Census Division of Statistics Canada is responsible for taking censuses.
Conducting a census involves four major stages. First, the census agency plans for the census and determines what information it will collect. Next, it collects the information by mailing questionnaires and conducting personal interviews. Then the agency processes and analyzes the data. Finally, the agency publishes the results to make them available to the public and other government agencies.
|A||Planning the Census|
Census agencies must begin planning for a census years in advance. One of the most important tasks is to determine what questions will appear on the census questionnaire. Census agencies usually undertake a lengthy public review process to determine the questions to be asked. They conduct public meetings, consider letters and requests from the general public, and consult with other government agencies and special advisory committees. In the United States, census questions must be approved by Congress and the Office of Management and Budget. In Canada, questions must be approved by the governor-general on the recommendations of the Cabinet.
The questions included on census forms vary from nation to nation depending on the country’s particular political and social history and current conditions. Most censuses request basic demographic information, such as the person’s name, age, sex, educational background, occupation, and marital status. Many censuses also include questions about a person’s race, ethnic or national origin, and religion. Further questions may ask the person’s place of birth; relationship to the head of the household; citizenship status; the individual’s or the family’s income; the type of dwelling the household occupies; and the language spoken in the household.
Questions that are routine in one nation may be seen as quite controversial in another, depending on the history of the country. The United States census does not ask about religious affiliation because such a question is considered a violation of the First Amendment right to freedom of religion or an invasion of privacy. Other nations, such as India, do collect such information. Questions on the number of children born to a woman were quite controversial in China in recent years because of government efforts to limit families to having only one child. In the United States, asking a question on income was considered controversial in 1940 when it was first asked. It is no longer considered as objectionable. Questions change in response to public debate about the state of society. For example, Americans wanted to know which households had radios in 1930, and the census introduced questions on housing quality in 1940. Canadians have recently begun to ask census questions on disability status and on the unpaid work done in the home.
Besides determining the content of the census, census agencies must make many other preparations. Staffing is a major concern for census agencies because censuses in most countries require a huge number of temporary workers to collect and process data. Consequently, census agencies must begin recruiting and training workers months or years in advance. For example, the U.S. Census Bureau had to fill 850,000 temporary, short-term positions to conduct the 2000 census. In order to hire and retain enough staff, it had to recruit nearly 3 million job applicants. The majority of temporary workers are hired to go door-to-door to interview households that do not respond to the census questionnaire. In some countries, government employees at a local level, such as schoolteachers, are asked to help conduct the count.
Prior to any census, a census agency must develop an accurate list of addresses and maps to ensure that everyone is counted. The U.S. Census Bureau obtains addresses primarily from the United States Postal Service and from previous census address lists. It also works closely with state, local, and tribal governments to compile accurate lists. Finally, census agencies often conduct an extensive marketing campaign before Census Day to remind the general population about the importance of responding to the census. This campaign may involve paid advertising, distributing materials by direct mail, promotional events, and encouraging media coverage of the census.
|B||Collecting the Information|
Until relatively recently, population censuses were taken exclusively through personal interviews. The government sent enumerators (interviewers) to each household in the country. The enumerators asked the head of the household questions about each member of the household and entered the person’s responses on the census questionnaire. The enumerator then returned the responses to the government. Today, many censuses are conducted primarily through self-enumeration, which means that people complete their own census questionnaire. Self-enumeration reduces the cost of a census to the government because fewer enumerators are needed to conduct interviews. In addition, the procedure provides greater privacy to the public and generally improves the accuracy of responses, because household members can take more time to think over the questions and consult their personal records.
A country conducting a census chooses a collection technique based on its social and political traditions and technological capacities. The United States census is highly automated and has been conducted primarily by mail since 1970. For the 2000 U.S. census, the Census Bureau offered many people the option of answering their questionnaires through the bureau’s Web site. Canada began to use self-enumeration in 1971. Today the Canadian government sends enumerators to deliver the census form to each household; the household head fills it out and sends it back to the government. In both the United States and Canada, enumerators are sent to follow up on households that do not mail back the census questionnaire. Other nations continue to conduct censuses only through direct enumeration. Some, such as Turkey, require people to stay home on Census Day to await the census taker.
Census agencies make a special effort to count people who may not receive a questionnaire by mail or who have no permanent address. For example, the U.S. Census Bureau sends census takers to interview people at homeless shelters, soup kitchens, mobile food vans, campgrounds, fairs, and carnivals. It consults with experts to find migrant and seasonal farmworkers. The bureau works with the Department of Defense and U.S. Coast Guard to identify people living on military installations or ships. The Census Bureau also counts military personnel and federal civilian government employees and their families who are living overseas. Finally, the agency distributes census questionnaires to people living in group quarters, such as college dormitories, nursing homes, hospitals, prisons and jails, halfway houses, youth hostels, convents and monasteries, and women’s shelters.
In the United States, Canada, and other countries, households receive either a short or long census questionnaire. Most households receive the “short form,” a brief set of questions on basic characteristics such as name, age, sex, racial or ethnic background, marital status, and relationship to the household head. But a small sample of households receives the “long form,” which asks many other detailed questions. These may include questions about the individual’s educational background, income, occupation, language knowledge, veteran status, and disability status as well as housing-related questions about the value of the individual’s home, the number of rooms and bedrooms in it, and the year the structure was built. The statistical technique of sampling—asking questions of only a representative sample of the population—allows census agencies to collect this detailed information without placing an undue burden on the population or creating an excessive cost to the government. About one in six households in the United States and one in five households in Canada receives the long form. These sample sizes are large enough to produce reliable information about the population characteristics of neighborhoods, regions, states or provinces, and the country as a whole.
|C||Processing and Analysis of Data|
For most of the 19th century in the United States and Canada, census data were tabulated and compiled by hand, without the aid of machines. Manual processing was very slow, and some figures were obsolete by the time they were published. The invention of mechanical tabulating devices in the late 19th century made processing of the data much faster and improved the accuracy of the results. Today, census questionnaires are processed primarily on computers and electronic equipment. Besides speeding the processing of results, computers have made it possible to perform sophisticated analyses on the data and to draw correlations between various social and economic characteristics of the country. For example, using census data, statisticians can easily determine the number of people living in Houston, Texas. But they can also determine the number of Houston women between the ages of 25 and 30 who have completed high school and are currently employed.
To process the data from hundreds of millions of paper questionnaires, the U.S. Census Bureau employs an advanced system that scans every questionnaire into an electronic image. Then the images are analyzed by computer software that can recognize when a check-box item on the questionnaire has been marked with a pencil or pen. Optical character recognition software analyzes handwritten responses on the questionnaire and translates them into electronic data. Once in electronic form, the data can be analyzed and turned into statistics. Unreadable or ambiguous responses are checked by census clerks and manually keyed into the computer.
|D||Publication of Results|
U.S. and Canadian censuses publish only general statistical information and keep individual responses confidential. By law, the U.S. Census Bureau and Statistics Canada are prohibited from releasing individual responses to any other government agency or to any individual or business. Census workers in both countries must swear under oath that they will keep individual responses confidential. Employees who violate this policy face a monetary fine and possible prison term. If an individual’s personal data were not kept confidential, people might refuse to participate in the census for fear that their personal information would be made public or used by the government to track their activities. In the United States, individual census responses are stored at the National Archives. After 72 years, the original forms are declassified and opened to the public. These original responses are frequently used by people researching the history of their families or constructing genealogies. In Canada, census responses from 1906 and later are stored at Statistics Canada. Microfilmed records of census responses from 1901 and earlier are stored at the National Archives of Canada; these are the only individual census responses currently available for public use.
Until the 1980s, census agencies published their results in large volumes of numeric tables—sometimes numbering in the hundreds of volumes. Today, the majority of census data is distributed electronically, either through the Internet or on CD-ROM, diskette, or magnetic tape. The Web sites of the U.S. Census Bureau and Statistics Canada provide online access to hundreds of statistical publications and data sets. The U.S. Census Bureau planned to disseminate results from the 2000 population census primarily via its Internet site. Both the U.S. Census Bureau and Statistics Canada continue to distribute printed publications for the most commonly requested demographic information. The Statistical Abstract of the United States, published annually by the Census Bureau, is an important statistical compendium on the social, political, and economic aspects of life in the United States. This publication includes data from decennial censuses as well as from other sources, such as surveys taken between censuses. Statistics Canada publishes a similar annual volume on Canadian statistics called the Canadian Year Book.
|IV||UNITED STATES CENSUSES|
A census of U.S. population has been conducted every ten years since 1790, as mandated by Article I, Section 2 of the Constitution of the United States. The U.S. Census Bureau, established in 1902, conducts the census. Before 1902 a separate office was set up for each census and then disbanded when the census was completed.
During the American Revolution (1775-1783), the leaders of the independence movement faced many problems uniting the 13 separate American colonies under a national government. Among these problems were how to allocate political representation among the states and how to levy taxes. The initial government structure under the Articles of Confederation, adopted in 1781, gave each state one vote in Congress. However, this system proved unsatisfactory to states with larger populations, who felt they deserved more representation than smaller states. A new Constitution, adopted in 1789, created a two-house legislature consisting of a Senate and a House of Representatives. Each state received two seats in the Senate regardless of population, but representation in the House of Representatives was based upon the population of each state. The decennial census was designed to provide the population figures for apportioning the seats in the House. Taxes levied on the states were also to be apportioned on the basis of population.
In the late 18th century, when a racially based slave labor system existed in the United States, almost 20 percent of the American population was enslaved African Americans. The framers of the Constitution debated whether slaves were “persons” or “property” and, thus, whether states should receive representation for their slave populations. The southern states, where slavery dominated, did not consider slaves as people for purposes of apportioning their state legislatures, but they did consider slaves as property for tax purposes. The framers could not find an easy solution to this dilemma and developed what came to be called the Three-Fifths Compromise. This clause in the Constitution required the census to count each slave as three-fifths of a person when determining the apportionment of the House. The Three-Fifths Compromise thus required the census to count the slave population and the free, mainly white, population separately. The Constitution also specified that “Indians not taxed,” that is, those American Indians who were not considered part of civil society, were not to be counted in the census.
The first U.S. census was taken in 1790 under the direction of Secretary of State Thomas Jefferson. Assistant U.S. marshals were instructed to travel the country and ask six questions at each household: the name of the family head; the number of free white males 16 and over; the number of free white males under 16; the number of white females; the number of other free people (nonwhite); and the number of slaves. The assistant marshals faced several challenges. Maps of the new nation were scarce, town and county boundaries were vague or unknown, and many untrusting citizens were uncooperative. There were no standardized questionnaires, so the assistant marshals had to supply their own paper, a substantial expense at the time. The census was completed in 18 months. It revealed a population of 3.9 million people in the 14 states plus the Southwest Territory, which later became Tennessee. At the time, Massachusetts included what is now Maine, and Virginia included what is now Kentucky.
For the next 50 years, the census questions remained basically unchanged. There were tentative efforts to begin to collect data on the economic situation of the society, with a manufacturing census in 1810 and the first census of occupations in 1820. These efforts met with only limited success, and Congress, dissatisfied with the results, did not repeat the questions in 1830. The 1830 census marked the first use of uniform printed schedules (forms), but not until 1850 did Congress mandate a census schedule with a line of questions for each person, including the person’s name. Before then the census captured the characteristics of entire families rather than individuals.
In later years, the census became more elaborate, with more questions asked and more data published. By 1860, six separate census questionnaires posed 142 different questions covering population, health, mortality, literacy, occupation, income, agriculture, manufactures, mining, fishing, commerce, banking, insurance, transportation, schools, libraries, newspapers, crime, taxes, and religion. The 1860 census collected so much information that some could not be published before the next census took place. In 1880, when the American population topped 50 million residents, the census was still compiled by hand, using a primitive tally system. The results from the 1880 census took eight years to tabulate and publish.
|C||Breakthroughs in Automation|
Automated tabulation of census data was made possible by the inventions of Herman Hollerith, an American engineer. In the 1880s Hollerith invented a machine that tabulated information on punched cards. The U.S. government used his machines for the 1890 census. Census clerks converted each person’s answers on the questionnaire to holes punched in a card, then ran the cards through the tabulating machines. The results were completed in only one year. Hollerith’s machine marked the beginning of modern data processing and led to further innovations in tabulating large amounts of data. His Tabulating Machine Company, founded in 1896, merged with other companies in 1911 to become the Computing-Tabulating-Recording Company, which in 1924 became International Business Machines Corporation (IBM).
In the late 1940s, the Census Bureau commissioned the construction of a computer for mass statistical calculations, UNIVAC I (Universal Automatic Computer). The UNIVAC was the first commercial, nonmilitary computer in the United States. Although UNIVAC accelerated processing of census data, it still required card punching for data input, a time-intensive task. By the late 1950s, the Census Bureau dispensed with the punch cards and, working with the National Bureau of Standards, developed the film optical scanning device for input to computers (FOSDIC), an electronic scanning system. FOSDIC scanned census questionnaires onto microfilm, then read the marks on the microfilmed questionnaires and transferred the data to computer tape. For information on modern processing methods, see the subsection Processing and Analysis of Data in the Conducting a Census section of this article.
The Census Bureau first used the statistical technique of sampling (collecting certain data from only a small sample of the population) in the 1940 census. This technique allowed the bureau to gather detailed information at a reduced burden to the public. In 1960 the bureau experimented with a mail census. The Census Bureau developed automated address files for the country, and in 1970 the American census was conducted primarily by mail. Today, more than 90 percent of residential addresses in the United States receive the census form in the mail. In the 1990 census, only 65 percent of households that received a census form in the mail returned it. Beginning with the 2000 census, the Census Bureau offered an “Internet Form,” which gave recipients of the paper short form the option to submit their answers via the bureau’s Web site. In the 2000 census, 67 percent of households returned a census form, reversing a three-decade decline in response rates.
Today, the decennial census of population and housing is taken in years ending in 0. An economic census is conducted every five years, in years ending in 2 and 7. The economic census is the major source of facts about the structure and functioning of the U.S. economy. It covers a wide variety of industries, such as manufacturing, mining, utilities, construction, transportation, information, finance and insurance, real estate, health care, educational services, and arts and entertainment. Separate censuses of agriculture and governments are conducted at the same time as the economic census. (Since 1997 the census of agriculture has been conducted by the U.S. Department of Agriculture.) Between censuses, the Census Bureau conducts periodic sample surveys to collect information about the population. For example, the monthly Current Population Survey collects information from about 50,000 households.
The Census Bureau also updates the information from the decennial census in the American Community Survey (ACS). This survey collects data from a sample of American households every month instead of only once each decade. Begun in 1996 on a small demonstration scale, the ACS has been greatly expanded since 2003 to provide yearly data on households. The Census Bureau is now able to bring together the monthly information from the ACS to release tabulations on households for all U.S. congressional districts and counties, cities, and American Indian/Alaska native areas with populations of 65,000 or more. Data for smaller geographic areas are compiled and reported on a two-to-five-year basis. Data for people who live in group quarters and who would not be counted as part of households will be added in coming years. The information gathered includes age, race, ethnic origin, education, marital status, veterans, disability status, and U.S. citizenship. The 2005 results, announced in 2006, reflected a sample of about 250,000 addresses per month, and showed a notable growth in immigrants, from 11.2 percent of the nation's population in 2000 to 12.4 percent.
Under federal law, the Census Bureau must deliver state population counts from the decennial census to the president of the United States by January 1 of the year following the census. The counts are used to reapportion seats in the House of Representatives. The bureau must deliver population totals for all counties, cities, and other political divisions to each state legislature within one year of the census. States and local governments use these data to draw legislative and other district boundaries.
National censuses were conducted in Canada every ten years beginning in 1851. Since 1956, they have been conducted every five years. In the provinces of Manitoba, Saskatchewan, and Alberta, censuses have been taken every five years since 1906. Statistics Canada, the national statistical agency, conducts all national censuses.
The first census in what is now Canada was conducted in 1665 and 1666 by French official Jean Baptiste Talon, who was sent by King Louis XIV to administer the colony of New France. Talon organized a door-to-door enumeration of the colony’s inhabitants, many of whom had settled in the towns of Montréal, Trois-Rivières, Cap-de-la-Madeleine, and Québec. The census counted 3,215 people and recorded each person’s name, age, sex, place of residence, marital status, and occupation. In 1667 Talon gathered information on livestock owned and land under cultivation. Talon’s census is sometimes considered the first modern census because it provided such complete information. A total of 36 censuses were conducted during the French regime, ending with the census of 1739. These censuses added questions on buildings and dwellings, agricultural output, and industrial output. Further censuses were conducted after the onset of British rule in 1763, including annual censuses of Upper Canada and Lower Canada from 1824 to 1842.
Regular decennial censuses began in Canada in 1851, when the province of Canada was still controlled by the British Empire. The British North America Act of 1867 transformed Canada into a federation known as the Dominion of Canada. The act required that the census provide population counts so that representation in the House of Commons could be apportioned among the four provinces of Ontario, Québec, Nova Scotia, and New Brunswick. The counts would also serve for periodic readjustment of the boundaries of electoral districts.
The first census of the Dominion, taken in 1871, counted 3.7 million people. The census questionnaire was made available in English and French, a tradition continued in every census that followed. The 1871 census was a very elaborate affair, collecting information not only on population but also on agriculture, livestock, animal products, industrial establishments, forest products, shipping and fisheries, mining, and public institutions. Canada was primarily an agricultural nation at the time, and the census was conducted by the Department of Agriculture.
In 1905 the census bureau was made a permanent government agency in the Agriculture Department. In 1918 the government created a Dominion Bureau of Statistics, which had responsibility for taking the census and collecting other statistical information about Canada. The bureau was renamed Statistics Canada in 1971.
The Canadian census first used the technique of sampling in the 1941 census, gathering additional information on housing from one household in ten. In 1956 it introduced a quinquennial census (a census conducted every five years). Censuses were conducted by personal interview until 1971, when households were asked to fill in their own questionnaires. In the 1996 census, 98 percent of households mailed back their census questionnaire; only 2 percent of households were enumerated by personal interview. In the 1990s, the Canadian census began adjusting its results to correct for people who were missed or counted twice in the census. The adjustment is based on studies conducted after the census that examine samples of households and people and determine if they were counted accurately.
Federal law in Canada requires the government to conduct censuses of population and agriculture every five years. These censuses are conducted in years ending in 1 and years ending in 6. Questions about housing are incorporated into the population census. An annual survey of manufactures collects information on more than 200 different industries in Canada.
|VI||PROBLEMS IN CENSUS TAKING|
Censuses provide important information about the population of a country. But they can become embroiled in political or social controversy simply by reporting information. Complaints about the census generally involve concerns about the accuracy of the count, the propriety of particular questions, and the uses to which the data are put.
All censuses contain errors of various kinds. Some people and addresses are missed. People may misunderstand a question or fail to answer all the questions. Census officials have developed elaborate procedures to catch and correct errors as the data are collected, but some errors remain. For example, the 1990 U.S. census missed 8.4 million people and mistakenly counted 4.4 million people, according to Census Bureau estimates. The latter figure included people counted more than once, fictitious people listed on forms, and fabrications by enumerators. Such errors undermine the credibility of the census as a mechanism for allocating seats in legislative bodies and government funds.
In recent years, developments in statistical analysis have made it possible to measure the accuracy of censuses. Census results may be compared with population information from other sources, such as the records of births, deaths, and marriages in vital statistics. Census officials can also determine the level of accuracy of the count by conducting a second, sample count called a post-enumeration survey or post-censal survey. In this technique, census staff knock on the door of each housing unit in selected blocks around the country, regardless of whether the housing unit was on the master address list. The staff member determines whether the household was counted in the census. By comparing the results from this survey with the census records, census officials can estimate how many people from each geographic region were missed in the original census count. Some nations, such as Canada and Australia, have begun to adjust the census results for omissions and other errors.
In the United States, city dwellers, the poor, non-English speakers, and ethnic minorities tend to be undercounted relative to the rest of the population. For example, the 1990 census missed an estimated 4.4 percent of African Americans but missed only 0.9 percent of whites. Beginning with the 1970 census, officials representing undercounted populations have claimed that their constituents have suffered loss of political representation and government funding because the apportionment and funding formulas are based on incorrect data. Mayors and leaders of civil rights organizations filed lawsuits to press for adjustment of census results based on statistical sampling.
In 1999 the Supreme Court of the United States ruled that population figures adjusted by sampling may not be used for reapportionment, the determination of how many seats each state receives in the House of Representatives. Reapportionment must use population figures based on the traditional head-count method. However, the Court left open the possibility that states could use the statistically adjusted population figures for redistricting, the redrawing of boundaries for congressional and state legislative districts. The Court’s decision also suggested that federal agencies and policymakers could allocate federal funds to state, local, and tribal governments based on the adjusted figures. For the 2000 census, the Census Bureau planned to produce two sets of population figures: one set of unadjusted data for the purposes of congressional reapportionment, and a second set of data statistically adjusted to correct for the undercount if deemed more accurate. In March 2001 the Census Bureau reported it could not certify the adjusted results as more accurate by the April 1 deadline to provide population figures to the states for redistricting. At the direction of Commerce Secretary Donald Evans, the bureau provided states with unadjusted data for redistricting.
Concerns about the confidentiality of the census represent another source of data error. Censuses require public understanding, support, and cooperation to be successful. Concerns about government interference with private life can prevent people from cooperating with what is essentially a voluntary counting process. People may be suspicious of giving information to a government agency or may object that particular census questions invade their privacy. When public trust is lacking, people may not participate. Census agencies in the United States and Canada are required by law to keep individual responses confidential. Nevertheless, individuals living in illegal housing units, undocumented immigrants who do not reside in the country legally, or individuals who do not wish to reveal their economic or social situation to a government agency are often reluctant to respond to a census.
Some people believe that censuses should not be conducted at all because the responses might fall into the wrong hands. During World War II (1939-1945), for example, the German Nazi forces occupying The Netherlands used the country’s census records and population registration data to identify Jews for detention, removal, and extermination. This use ultimately undermined the legitimacy of the census after World War II. In The Netherlands, the legacy of the Nazi era was one of the major justifications to end census taking. The Netherlands took its last regular census in 1971 and now collects population information through other mechanisms.
Censuses have been taken since ancient times by emperors and kings trying to assess the size and strength of their realms. These early censuses were conducted sporadically, generally to levy taxes or for military conscription. Clay tablet fragments from ancient Babylon indicate that a census was taken there as early as 3800 bc to estimate forthcoming tax revenues. The ancient Chinese, Hebrews, Egyptians, and Greeks also conducted censuses. However, enumerations did not take place at regular intervals until the Romans began a count of their empire’s inhabitants. Among the Romans the census was usually a count of the male population and assessment of property value. It was used mainly for drafting men into military service and for taxing property.
After the fall of the Roman Empire in the 5th century ad, census taking disappeared for several hundred years. The small feudal communities of the Middle Ages had neither the mechanisms nor the need for censuses. However, in 1086 William the Conqueror ordered the compilation of the census-like Domesday Book, a record of English landowners and their holdings. From the data given in this survey, which was made to determine revenues due to the king, historians have reconstructed the social and economic conditions of the times.
The modern census dates from the 17th century, when European powers wanted to determine the success of their overseas colonies. Thus the British crown and the British Board of Trade ordered repeated counts of the colonial American population in the 17th and 18th centuries, starting in the 1620s in Virginia. The first true census in modern times was taken in New France, France’s North American empire, beginning in 1665. The rise of democratic governments resulted in a new feature of the census process: The 1790 census of the United States was the first to have its results made public. For more information on the history of censuses in the United States and Canada, see the United States Censuses and Canadian Censuses sections of this article.
Sweden began to conduct censuses in the mid-18th century, and England and Wales instituted a regular decennial census in 1801. During the 19th century and the first half of the 20th century, the practice of census taking spread throughout the world. India conducted its first national census in 1871, under British rule. China’s first modern census, in 1953, counted 583 million people.
The United Nations encourages all countries to conduct censuses. It also promotes adoption of uniform standards and census procedures. The United Nations Statistical Office compiles reports on worldwide population.