United States census is an extensive nationwide information-gathering project conducted by the U.S. federal government. The U.S. Census Bureau, an agency of the Department of Commerce, conducts a census of population and housing every 10 years. Because of its 10-year cycle, the U.S. census is called a decennial census. The Census Bureau also conducts censuses of agriculture, which gather such information as the number of farms and farmworkers; governments, which collect information on units of local government; and economic activity, which collect data on the output and resources of various industries.
Census taking, also called enumeration, enables the government to obtain a current description of the society it governs. This description includes the size of the population, as well as such facts as age, employment, ethnicity, housing, income, race, and sex. Census information helps government agencies develop and administer programs, distribute funds, and examine social and economic problems. It also determines the number of representatives each state will have in the U.S. House of Representatives. Businesses and other organizations have additional uses for census information. For example, business people may use a census to determine where they can find a skilled and educated labor force to staff new factories and plants.
Obtaining and using census information
Planning, conducting, and processing the U.S. census is a difficult and expensive project. Planning usually begins while the previous census is still underway. The Census Bureau evaluates all phases of the previous census, assesses new technologies, and asks for advice on future needs for information. The bureau must determine census content, prepare field procedures for taking the census, select processing procedures, and set timetables and formats for issuing census information.
Census content.
The Census Bureau, with the approval of the Office of Management and Budget and of Congress, determines the content of each census. Before choosing the topics, the bureau consults many public and private groups that use census information. Agencies at all levels of government—federal, state, and local—have the greatest influence on the choice of topics. Other users of census data, including business executives, educators, and researchers, work with the Census Bureau through advisory committees. These committees meet regularly with bureau specialists to discuss census needs and uses. The bureau also holds public meetings in every region of the country.
After selecting the topics to be covered, the Census Bureau develops questions that will obtain the desired information. The bureau conducts many studies to test whether new questions produce useful responses. For example, every decade it is necessary to redesign questions on race and ethnicity, because of changes in population and in how people refer to their ethnic heritage. For each census, a few questions are added, dropped, or rephrased.
Taking a census of population.
The Census Bureau uses a combination of self-enumeration procedures and enumerators in conducting censuses. In self-enumeration, individuals fill out the census forms for themselves and other members of their household. Households can complete the census either online, by phone, or by returning a paper questionnaire.
Enumerators are individual census takers who go door to door to find housing units, to leave census forms to be mailed back, and in some cases to collect information. Personal contact is necessary in areas where households do not have standard addresses or do not get mail. Enumerators are also used in areas where language barriers, poverty, distrust of government, or other reasons make the standard mailing procedure ineffective. In addition, enumerators are needed to contact people who do not return their forms on time or who make mistakes in completing the forms.
The Census Bureau must also contact U.S. citizens who live outside the United States, including military personnel, employees of the federal government, and their families. The bureau must get information about people in prisons, nursing homes, shelters for the homeless, and other special residences as well.
Sampling
involves surveying a carefully selected portion of the population and then using the findings to estimate information for the total population. Sampling methods can generate a large amount of information while reducing costs and minimizing the burden on the public.
From 1940 to 2000, for instance, every household was asked to complete a short form that asked a small number of basic questions. In addition, some households were asked to complete a longer form with additional questions. The longer form was a sample survey within the census. In 2005, the bureau replaced the longer form with a sample survey that collects certain data annually.
Sample surveys provide more detailed information on a wider range of topics than can be included in a census. For a survey of thousands of households, a census bureau can use a highly trained staff and maintain tight administrative oversight over all phases of data collection and processing. Using scientific methods for designing a sample and projecting results to the total population, the staff can keep sampling errors small.
Publishing census information.
Basic census information for counties, states, and other locales is printed as bulletins or volumes. Tables of census information also appear on the bureau’s internet website, with a range of additional data that cannot fit in printed tables. In printed tables, census officials choose the age groups, racial categories, and income ranges used. On the website, users can choose their own combinations of subjects and geographical areas.
The bureau follows special procedures to make sure personal records stay confidential. Concern that census taking might invade privacy led the U.S. Congress to guarantee the confidentiality of personal information. The bureau withholds personal identification data, such as names and addresses, when it feeds information into the computers. By law, only bureau employees may examine census records. The bureau cannot share census information on individuals with other government agencies. For instance, census responses may not be used by the Internal Revenue Service for determining taxes or by immigration officials to determine legal status.
Seventy-two years after a census is taken, the names and other confidential facts it includes are made available to the public. Genealogists (people who study family trees) and others interested in family and local history find this information helpful.
Using census information.
Census information helps government agencies administer programs, distribute revenues, study social and economic problems, evaluate policies, and plan activities. The statistics provided by a population census affect the assignment of funds for economic development, housing, education, medical care, and social security. Population size determines the number of representatives each state may have in the U.S. House of Representatives. Membership in state legislatures is also determined on the basis of population. Economic censuses tell much about the nation’s changing economic condition. Agricultural censuses provide a picture of the nation’s farmers, agricultural production, and resources.
Business leaders study census figures in making such decisions as where to locate new facilities, where to direct their advertising, and how to plan production. The construction industry uses census data to decide where to build new housing. Utility companies determine service requirements on the basis of census data. Nongovernment organizations and community groups use census information to identify problems, track progress, and evaluate programs.
Census statistics also help social scientists analyze economic and social problems and plan solutions. These experts study census statistics on such subjects as marriage and divorce, population movement, geographic locations of older people, and the relationship of education to income and employment.
The history of the U.S. census
Census taking is one of the oldest activities of the United States federal government. The Constitution of the United States requires that a state’s representation in the House of Representatives be based on its population. To meet this requirement, the nation has conducted a population census every 10 years since 1790.
The first U.S. censuses were simple population tallies. Later censuses were expanded to collect information on employment, housing, and other matters. At first, federal marshals collected the data. Later, as the country grew and censuses gathered more information, the government created a permanent agency responsible for the census. Advances in computing technology have been pioneered to aid in processing census data. Because the results of the census directly affect political representation, census-related disputes have frequently arisen.
The Constitution and the census.
Article 1 of the U.S. Constitution calls for a census to be taken every 10 years to determine how many political representatives each state should get in the House of Representatives:
Representatives and direct taxes shall be apportioned among the several states which may be included within this Union, according to their respective numbers, which shall be determined by adding to the whole number of free persons, including those bound to service for a term of years, and excluding Indians not taxed, three-fifths of all other persons. The actual enumeration shall be made within three years after the first meeting of the Congress of the United States, and within every subsequent term of ten years, in such manner as they shall by law direct.
The census provided a solution to one of the fundamental political controversies of the American revolutionary era: how to allocate (distribute) legislative representation fairly among the states. Under the Articles of Confederation, which were adopted in 1781, states voted as units, regardless of how big or small the state was. Virginia, then the biggest state, cast the same vote as such smaller states as Rhode Island and Delaware.
At the Constitutional Convention of 1787, delegates from the large states sought to change the voting arrangement. These delegates argued in favor of the Virginia Plan, under which population would determine the number of representatives a state could send to the national legislature. The small states supported the New Jersey Plan, which proposed that all the states would have an equal number of representatives. The Connecticut delegates suggested a compromise that settled the problem. Their plan provided for equal representation in the Senate, along with representation in proportion to population in the House of Representatives. This proposal became known as the Connecticut Compromise or the Great Compromise.
The Constitution also tied the Electoral College—the group that elects the president—indirectly to the census. Each state’s representation in the Electoral College would equal its number of Senate seats plus its number of House seats. Finally, the Constitution accounted for populations growing and shifting over time. By taking a census every 10 years, legislative apportionment (assignment of seats in a legislature) could be revised to match the changes in the country.
Using population as a measure for apportionment was complicated by the issue of slavery. At the time the Constitution was written, about 20 percent of the American population was enslaved African Americans. If simple population were used as the apportionment measure, should the Southern States be granted political representation for their slaves even though slaves had no political rights? Northern States were already beginning to abolish the institution of slavery, and they opposed including slaves as part of the population to be counted. Southerners insisted that slaves be counted as part of the population, thereby increasing Southern political representation. The solution to the dilemma came to be known as the three-fifths compromise. Slaves were to be counted in the census, but the slave population totals for each state were to be reduced to three-fifths of the actual number when calculating the state population totals for apportionment.
Apportionment was further complicated by the question of how to count American Indians. At the time the Constitution was written, American Indian tribes were considered sovereign powers. Article 1 created the category of “Indians not taxed”—American Indians who lived as part of a tribe within the boundaries of the United States. “Indians not taxed” thus became the one population group specifically excluded from being counted in the U.S. census.
Early censuses.
The censuses from 1790 to 1840 were simple counts of people in each household. There was no permanent census agency. Congress instructed U.S. marshals to appoint assistants to gather the census data. The assistants contacted the head of each household to collect the needed information on the people in the household. The first census reported the name of the head of each household; the number of free white males aged 16 and over; the number of free white males under age 16; the number of free white females; the number of “other free persons”; and the number of slaves. Households formed the basic census unit in the early censuses. No information was collected on specific individuals except for the name of the head of the household.
The marshals tallied the totals from their assistants and sent the results to the secretary of state. No system existed to check the results at any level. Congress asked only that the census takers take an oath that they had faithfully counted everyone. Returns for each area were posted in a public place where anyone could review them. Most of the nation was not densely populated, and it usually took about a year to conduct a census. Congress frequently had to legislate extra time for the marshals to collect the information. Despite these difficulties, censuses proved to be a success. The population was counted, and Congress was reapportioned, just as the framers of the Constitution had intended.
During the early 1800’s, a number of changes were made in census procedures and questions. In 1820, the census recorded the age and sex of the free black and slave populations for the first time and collected some basic information on occupations. In 1830, the State Department provided census takers with printed, standardized forms.
As the nation expanded westward, reapportionment based on the census helped states receive political representation in proportion to their population. By 1820, several of the original 13 states began to lose seats in the House. By 1840, the Senate had a majority of Western members. By the beginning of the American Civil War in 1861, Western members also dominated the House.
The census and the Civil War.
By the 1820’s, the population of the Southern States was not growing as fast as that of Northern States. Between 1790 and 1860, the South’s share of seats in the House of Representatives fell from 46 percent to 35 percent. The South’s loss of political power focused increased attention on the census process.
Congress instituted the first major reforms of the census process in preparation for the census of 1850. Responsibility for the census shifted from the secretary of state to the newly created Department of the Interior. A formal post of census superintendent was created. A wide variety of new questions were added to the census form, including questions on place of birth, occupation, and literacy. With the 1850 census, the individual, rather than the household, became the basic census unit. In addition, census figures were now tallied by a Census Office in Washington, D.C., rather than locally.
The 1860 census was completed a few months before the Civil War broke out. The census results illuminated some of the contrasts between the North and the South. For example, the census showed that 26 percent of Northerners lived in urban areas as opposed to only 10 percent of Southerners. It also reported that 95 percent of the country’s black people lived in the South. In addition, because of population changes and reapportionment, Southerners anticipated a further decline in political power and expected that they would face more losses in the House in the future. Northerners, on the other hand, approved of the census and apportionment process because it worked to their political advantage.
After the end of the Civil War in 1865, Northerners learned that the census and reapportionment could work to their political disadvantage. The Thirteenth Amendment to the Constitution abolished slavery and ended the three-fifths compromise. As a result, the Southern States stood to gain increased representation in Congress because the population of former slaves would no longer be reduced to three-fifths of its total when allocating House seats.
At first, few politicians expected the freed slaves to be able to vote. But Northern Republicans soon realized that if former slaves could not vote, Southern States would gain seats in the House and Southern Democrats would still win the seats. Because the number of votes a state had in the Electoral College depended on the number of seats it held in the House, Northern Republicans feared that Democrats might gain control of the presidency as early as 1868. These concerns encouraged Congress to grant important political and civil rights to the former slaves. The Fourteenth Amendment promised citizenship, due process, and equal protection of the laws to “all persons born or naturalized in the United States.” It also threatened to reduce the representation of any state that did not grant voting rights to all of its male citizens. The Fifteenth Amendment declared that the right to vote “shall not be denied or abridged by the United States or by any state on account of race, color, or previous condition of servitude.”
In 1870, “Indian” was added to the list of races on the census form. “Indians not taxed” were still omitted from the count, but Indians living apart from their tribes were counted and identified as “Indian” in the race question. The 1890 census was the first to count the entire Indian population. However, the count of “Indians not taxed” was kept apart from that for the rest of the nation. In 1924, Congress granted citizenship to all Indians, and the census began counting all Indians as part of the nation’s total population.
Population growth and the census.
After the Civil War, the American population continued to grow and spread rapidly. As the 1890 census results were tallied, the census superintendent announced the closing of the frontier—that is, maps based on population no longer showed a clear western boundary beyond which lived fewer than 2 persons per square mile (0.8 person per square kilometer). At the same time, the census revealed rapid urban growth across the nation. Cities replaced the rural West as the places of most rapid growth. European immigrants, as well as people born in rural parts of the United States, flocked to the new jobs and opportunities offered by cities. States in the Northeast and Midwest swelled with immigrant populations drawn to cities and to industrial jobs.
Congress continued to add seats to the House of Representatives after every census. In 1860, the House held 243 members; by 1910, there were 435. As the country continued to grow, each House member represented more and more people.
In the late 1800’s and early 1900’s, Congress added more questions to the census and called for new tables of published data. Changes for the 1870 census included maps to guide census takers and limits on what census data could be disclosed. In 1880, U.S. marshals were replaced by local census supervisors, a temporary position with the sole duty of conducting the census.
The 1890 census pioneered the use of machine tabulation, technology that eventually led to modern computers. Previously, clerks in Washington or census takers in local areas manually counted and tallied census data. In 1890, the Census Office began using a mechanical system invented by an American businessman named Herman Hollerith. The new tabulating machines—along with more employees—allowed the Census Office to publish much more information from each census.
Censuses from 1840 to 1900 were conducted by a temporary Census Office that disbanded after results had been published. In 1902, Congress made the Census Office a permanent government bureau. It joined the new Department of Commerce and Labor in 1903. Today, the Census Bureau remains in the Department of Commerce.
Refusal to reapportion.
The 1910 census was the first conducted by a permanent census department. Reapportionment brought the number of representatives in the House to 435, about as many representatives as the House chamber was capable of holding. Some politicians argued that no more representatives should be added, regardless of results of future censuses.
An apportionment crisis occurred after the 1920 census, which showed that a majority of Americans lived in urban areas. The large urban states—primarily in the Northeast and Midwest—stood to gain the most from reapportionment. Congress, which was still controlled by rural politicians, refused to pass a reapportionment bill. Leaders from rural areas argued that urban states should not get representation for their foreign-born populations, many of whom were not citizens. Urban legislators could not overcome this resistance, and Congress was not reapportioned, the only time in U.S. history this has happened.
In 1929, however, Congress passed a bill to reapportion the House in 1932 using the results of the 1930 census. But passage of the bill required a compromise. The long-standing requirement that congressional districts be of equal size was abandoned, and the number of seats in the House was limited to 435. The result redistributed political power among the states, but rural and small town control of Congress was preserved by the way districts were drawn.
In the 1930’s and 1940’s, new questions on household income, unemployment, and housing quality were added to the census form to help the government deal with the problems of the Great Depression and World War II (1939-1945). The 1940 census was the first to use statistical sampling. Several questions were added for about 5 percent of the people. Responses to the additional questions were used to project how the entire nation would have responded.
In 1951, the Census Bureau began using UNIVAC (UNIVersal Automatic Computer), the first large-scale electronic computer used outside the military. Census data came into use throughout the federal government as federal aid and grant programs increased. Sample surveys, sent to a representative sample of the population, were created as a way to collect information between censuses. The Census Bureau also set up quality controls to check the accuracy of the census count and responses to individual questions.
The reapportionment revolution.
The distortions created by the 1929 decision to abandon districts of equal size became clear by the 1960’s. Urban and suburban Americans were underrepresented in both their state legislatures and Congress. Challenges to the 1929 compromise began to appear in the nation’s courts. In 1962, the Supreme Court of the United States ruled in Baker v. Carr that voters could bring questions of unfair apportionment to federal courts. In a series of related decisions that followed, the Supreme Court developed the “one-person, one-vote” principle. As a result, districts for state legislatures, local legislative bodies, and Congress had to be “substantially equal” in population. By the late 1960’s, legislative districts had been redrawn according to the new guidelines. Legislative representation for underrepresented areas—mainly urban and suburban areas—increased dramatically.
The requirement that legislative districts be equal in population focused attention on the quality of the census data. Demographers (people who study population statistics) had discovered that the census counted some groups in the population better than others. Minorities, the poor, and those in urban areas were counted less accurately than those living in suburbs and more well-to-do areas of the country. Responding to the “one-person, one-vote” decisions, politicians began to scrutinize the census data for their districts. Those who believed their areas were undercounted or miscounted pushed to improve the data.
Improving census accuracy.
For the 1960 census, the Census Bureau began using a machine called FOSDIC (Film Optical Sensing Device for Input to Computers). Previously, workers read the completed census forms and created corresponding punch cards for the computer. FOSDIC used scanning technology to “read” the information on specially designed census forms into the computer.
The 1960 census also introduced separate short and long forms. Long forms included all the questions on the short forms plus additional queries. For example, both kinds of forms had questions on sex, race, and marital status. But the long form also asked about commuting, length of residence, and other matters. Long forms were distributed to about a fourth of all households.
The Census Bureau experimented with collecting some census data by mail in the 1960 census. In 1970, the majority of American households received their census forms by mail. Census officials only visited areas where the bureau did not have good mailing lists or where households did not mail back their forms.
For most of the 1970’s and 1980’s, the Census Bureau worked to improve the accuracy of the count. Congress, demographers, local politicians, and minorities all wanted to improve the accuracy of the census. They were chiefly concerned that a significant number of the population was being missed by the census, thereby leading to undercounts. One approach was to try to correct errors in the census after the count. Under this plan, the bureau would take a sample survey of the population a few months after the census. The results of this survey would then be compared to the count from the census, and the census numbers would be adjusted for undercounts.
However, Census Bureau plans to adjust census figures for undercounts led to a political battle that has not yet been resolved. Republicans generally oppose adjusting for the undercount, because they believe those areas that would gain population—and, therefore, gain representation—would vote Democratic. For the same reason, Democrats generally support adjusting for the undercount.
In the late 1980’s, Department of Commerce officials in the Republican administrations of Presidents Ronald Reagan and George H. W. Bush canceled the implementation of the new adjustment methods. New York City and a group of other cities, states, and civil rights organizations then sued the Commerce Department to try to force it to implement the new methods. The courts ordered that the new methods be implemented in 1990, but that the commerce secretary decide whether or not to use the corrected data as the official results. Republican Commerce Secretary Robert Mosbacher decided not to use the adjusted data. This decision was also contested, but it was upheld in the courts.
In the 1990’s, the Democratic administration of President Bill Clinton proposed that the 2000 census should be adjusted for the undercount. Republican congressmen and the Southeastern Legal Foundation sued to stop the Clinton plan. In 1999, the Supreme Court ruled that the current census statute barred the use of sampling and adjustment methods for calculating the apportionment of seats in Congress among the states. But the court also ruled that the census results should be as accurate as possible. As a result, the Census Bureau proceeded to take the sample survey in 2000 as well, and planned to release adjusted data if it could be shown to be more accurate.
In 2001, the Census Bureau reported that the sample survey results again showed an undercount of several million people. But the Republican administration of President George W. Bush decided against releasing adjusted census data. States and local governments unhappy with that decision again sued the Commerce Department to gain access to the adjusted data.
The battles over adjusting census results demonstrate the importance of the census in American political life. The census was designed as a tool for distributing political power fairly among the nation’s population. But because of its political importance, the census has frequently provoked heated controversy.
Recent censuses.
In 2010, the Census Bureau used a single list of questions called the short-form questionnaire. This questionnaire asks a small number of basic questions. It asks the same questions of all households. Previously, the Census Bureau had also used a long-form questionnaire. This questionnaire included additional social, economic, and housing questions. These questions were asked of only a sample of all households. The 2010 census was the first to count same-sex married couples.
For all censuses from 1960 to 2010, the Census Bureau mailed out lists of questions and asked the public to complete them and mail them back. In 2020, the bureau mailed out invitation letters and asked the public to respond to the census either online or by phone. They also mailed out questionnaires to some homes in areas with low internet access. The 2020 census was the first census to allow people to respond online.
Most households completed the census either online, by phone, or by returning a paper questionnaire. Although the self-response rate was high, it still left many households that had not returned their information. The bureau’s nonresponse follow-up program obtained the missing information. Due to the COVID-19 pandemic, the Census Bureau delayed nonresponse follow-up until later than in previous censuses.
The Census Bureau was originally scheduled to deliver state data to the president of the United States by Dec. 31, 2020. However, due to delays caused by the COVID-19 pandemic and some irregularities that the bureau discovered among the data, the Census Bureau was unable to meet this deadline. After processing the data it collected, the Census Bureau delivered state population counts to the president on Apr. 26, 2021.
See also Census; Census Bureau, United States; Hollerith, Herman; United States census of 2000 United States census of 2010 United States census of 2020.
