How the Census Works

U.S. Census Bureau director Robert Groves (seated) officially kicked off the 2010 Census by dogsledding to the first enumeration site in Noorvik, Alaska. Rural Alaskans are traditionally the first to be counted.
U.S. Census Bureau director Robert Groves (seated) officially kicked off the 2010 Census by dogsledding to the first enumeration site in Noorvik, Alaska. Rural Alaskans are traditionally the first to be counted.
U.S. Census Bureau

In a country as large as the United States, how is it possible to count each person in every state, city, county, prison cell and hospital bed? Every 10 years, this is the daunting task assigned to the Commerce Department's Census Bureau. The census is mandated by the U.S. Constitution and goes all the way back to 1790, when less than 4 million people — not counting slaves or Native Americans — lived in the fledgling nation. In 2010, the census recorded 308.7 million people, a 9.7 percent population increase from 2000, or roughly 79 times as many residents as 1790 [source: U.S. Census Bureau].

The main purpose of the census is to figure out how many seats each state receives in the House of Representatives. Since 1911, there have been 435 seats in the House, and each state is guaranteed at least one [source: U.S. House of Representatives]. Additional seats are apportioned by population, with the most populous states receiving the most seats. California, the winner in this category, has 53 seats in the House, while states like Delaware, Alaska and South Dakota only have one [source: U.S. Census Bureau].

But the census is much more than just apportioning seats. It's a once-a-decade chance to track the shifting demographics of America. How many people live in big cities? How many children live in each household? What is the nation's racial and ethnic breakdown? Federal and state governments rely on census data to budget for social welfare programs and design public transportation systems. Cities and private industry use demographic figures to plan hospital expansions and housing developments, and assess the need for new schools or new strip malls.

Every year, federal and state governments use census data to allocate more than $400 billion toward public services and infrastructure [source: U.S. Census Bureau]. Because this data is so important, all U.S. residents (regardless of immigration status) are technically required by law to faithfully and accurately fill out the census form. When Minnesota Congresswoman Michele Bachmann announced that she would only answer the first question on the 2010 census form — and not provide individual names, ages or ethnicities of household members — she risked a fine of $100 to $500 for breaking the law. A census spokesperson confirmed the fines to Politifact, but added that they are rarely enforced [source: Farley].

So how did the census come into being?

History of the Census

The concept of a census, or counting of residents, is an ancient one dating to biblical times – at least nine censuses are mentioned in the Bible. Some say the first census ever taken in North America was in 1576, 200 years before America gained its independence from the British. Spanish King Philip II who wanted information on some of his colonies and what taxes they paid sent American Indians through what is now Mexico with a list of 100 questions. The Indians spoke no Spanish, so they recorded the answers in hieroglyphs (pictures) and made maps the same way [source: Prescott Evening Courier]. Others say the first North American census was taken in Canada (in what was then New France) by Jean Talon on behalf of the king of France. Talon went door to door during the winter of 1665-66 and counted 3,215 people of European descent [source: Statistics Canada].

Since 1790, U.S. national census information has been taken every 10 years (in years ending in zero) because it is mandated by the U.S. Constitution and necessary to determine each area's representation in the U.S. House of Representatives. In 1790, George Washington signed the act into law. While the Constitution describes the census simply as an "enumeration of inhabitants," the census has evolved into a more comprehensive -- and useful – process for understanding the habits of people living in the United States.

According to Judy Hanna Green's book "Finding Treasures in the U.S. Federal Census," the primary goal of the original 1790 census was to provide information on men eligible for the military. On the heels of the Revolutionary War, the new American citizens were especially conscious of the importance of a strong military. Later, during the War of 1812, much of the 1790 census was destroyed by fire.

In the first national census, 650 U.S. marshals went house to house unannounced on horseback all over the nation to count people, writing with quill pens on any scraps of paper they could find. The cost of that first census project was $45,000 [source: Washington Post]. Compare that with the 2010 census which cost $13.1 billion, $1.6 billion less than anticipated [source: El Nasser and Copeland].

Technology and the Census

The pantograph  machine allowed census workers to use punch cards for the first time in 1890.
The pantograph machine allowed census workers to use punch cards for the first time in 1890.
U.S. Census Bureau

Census taking became more streamlined in 1880 when trained workers were employed for the first time. Technology followed in 1890. The Census Bureau developed a new electrical machine that could add up responses to questions after census workers punched holes in the right places for each answer. Cards were then fed into a machine that totaled the result. It was bulky but a great advance at that time -- anything that sped up the process was a help since some of the results have to be ready nine months after Census Day (more about that later).

The first modern computer, called ENIAC, was invented in 1946 at the University of Pennsylvania. This computer, which was really many machines working together, took up a whole room. The system was ready in time for use in parts of the 1950 census, and the Census Bureau ordered its own computer, called UNIVAC. That technology has advanced over the years and now high-speed, supercomputers assist with the census.

The major technological leap for the 2010 census was the use of handheld GPS devices to update the Census Bureau's master address list of the nation's 145 million residences. The accuracy of GPS coordinates allowed the bureau to assign each home, apartment or trailer to its appropriate Congressional district. In the past, armed only with paper maps, census workers accidentally assigned an average of 5 percent of American residences — particularly rural homes — to the wrong district. With the upgrade to GPS devices, the bureau projected a 0.05 percent error rate [source: Luhby].

The Census Bureau uses the National Processing Center and works with contractors who operate three processing centers responsible for a variety of data capture functions:

  • A full electronic data capture and processing system records an image of every questionnaire.
  • Questionnaires returned by mail are sorted automatically to ensure timely capture of critical information needed before the non-response follow-up.
  • Optical mark recognition is used for all check-box data items.
  • Intelligent character recognition (ICR) is used to capture write-in character-based data items.
  • A clerical keying operation captures and resolves difficult ICR cases.
  • A quality assurance review is conducted on data keying and scanning activities.

Most of the U.S. census was taken door-to-door until 1960, when census officials recognized the inefficiency of this method in dealing with such a fast-growing, mobile population. That's when they decided to use the mail to distribute forms. In the 2010 census, 74 percent of households returned their census forms by mail, and the remaining households were counted by an army of census workers. The 1.4 million workers hired in 2009 and 2010 for the census included the following positions:

  • Administrators -- They determine how each division of the Census Bureau will do its part in the census.
  • Enumerators -- 585,000 workers went door-to-door in 2010 to gather information from residents who did not mail in their census forms.
  • Statisticians -- They make sure the Census Bureau's math is right.
  • Demographers -- These people understand the statistics and have studied what statistics tell about American life. They analyze the census numbers, comparing them with numbers from earlier censuses, and tell us important things about the future.

Why Is the Census Important?

A painting showing a census taker, complete with quill pen, in the 1850 census.
A painting showing a census taker, complete with quill pen, in the 1850 census.
U.S. Census Bureau

Participating in the census is in everyone's best interest, because the information on the forms is used by decision-makers to determine which communities, schools, hospitals and roads need federal funding.

Here are just a few examples of important uses for census numbers:

  • The federal government uses census numbers to allocate more than $400 billion in federal funds annually for community programs and services, such as education programs, housing and community development, health care services for the elderly and job training.
  • State, local and tribal governments use census information for planning and allocating funds for new school construction, libraries, highway safety and public transportation systems, new roads and bridges, location of police and fire departments and many other projects.
  • Community organizations use census information to develop social service programs, community action projects, senior lunch programs and child care centers.
  • Businesses use the numbers to decide where to locate factories, shopping centers, movie theaters, banks and offices -- activities that often lead to new jobs.
  • The U.S. Congress uses the census totals to determine how many seats a state will have in the U.S. House of Representatives. In addition, states use the numbers to allocate seats in their law-making bodies.

If you need closer-to-home reasons for completing your census form, the Census Bureau suggests that you consider the following:

  • You can help your community thrive. Does your neighborhood have a lot of traffic congestion, or overcrowded schools? Census numbers help your community work out public improvement strategies. Nonprofit organizations use census numbers to estimate the number of potential volunteers in communities across the nation.
  • You can get help when you need it. Many 911 emergency systems are based on maps developed for the last census. Census information helps health providers predict the spread of diseases through communities with children or elderly people. And when disasters hit, the census tells rescuers how many people will need their help.
  • You can help American businesses. Census numbers help industry reduce financial risk and locate potential markets. This means that businesses can determine the marketability of potential products.
  • You can get information you and your family need. Although individual records are held confidential for 72 years, you can request a certificate from past censuses that can be used to establish your age, residence or relationship -- information that could qualify you for a pension, establish citizenship or obtain an inheritance. (Right now, your children may be using past census information to do their homework.)

Privacy and Security of Census Data

By law, the Census Bureau cannot share your answers with others, including welfare agencies, immigration, the Internal Revenue Service, courts, police and the military. Under the provisions of Title 13 of the U.S. Code, census workers who break this law face up to five years in prison and $250,000 in fines [source: U.S. Census Bureau]. The law works -- millions of questionnaires are processed without any breach of trust.

The law requires each batch of census forms to remain private for 72 years. This is to encourage honesty and accurate information. The rationale is that little negative impact could happen after 72 years, since most of the people listed would be gone. The process of microfilming and printing the census also takes a long time to accomplish by the sheer volume of documents. (This process usually takes another two years or so to complete and make ready for the public, according to bureau officials.) In 2012, the bureau released data from the 1940 census and posted it online through the National Archives.

The Great Recession of the late 2000s had a positive effect on finishing Census 2010. The bureau was able to tap into a large pool of unemployed but educated and experienced people to work on the census, which helped them finish the count faster than in previous years and save millions of taxpayer dollars [source: El Nasser and Copeland].

How Does the Census Process Actually Work?

An enmerator on the job in 1920. Until 1960, everyone was enumerated via personal interview. After that, mail was used. The 1920 census counted 106 million people living in the U.S.
An enmerator on the job in 1920. Until 1960, everyone was enumerated via personal interview. After that, mail was used. The 1920 census counted 106 million people living in the U.S.
U.S. Census Bureau

Collecting and reporting census data is a multiyear process. The 2010 census actually began back in 2008, when the bureau started recruiting workers for its local offices. From April through July 2009, 140,000 workers armed with GPS devices canvassed the country to confirm addresses on file [source: The Leadership Conference].

Data collection began in earnest on Jan. 25, 2010, where census workers counted residents in Noorvik, Alaska in person. Since 1990, rural Alaskan villages have been the first to be counted since this needs to happen before the spring thaw makes travel impassable [source: Miller]. Then in February, advance forms were sent to rural areas where census forms must be delivered in person [source: Durando]. In early March, U.S. residents received letters notifying them of the upcoming census. In this letter, residents were given the option of receiving census forms in five languages other than English — Spanish, Chinese (simplified), Korean, Vietnamese and Russian — or a bilingual Spanish/English form. By mid-March, census forms were mailed to 120 million U.S. residences [source: U.S. Census Bureau].

Even though the 2010 census form only had 10 questions, bureau officials knew that many residents, particularly foreign language speakers, would need help filling it out. The bureau provided online guides in 59 languages on the 2010 census Web site, telephone assistance in six languages, and staffed 30,000 in-person Questionnaire Assistance Centers across America [source: U.S. Census Bureau].

During March and April 2010, the Census Bureau conducted special operations to count people with no fixed address or who live in dormitories, nursing homes, prisons, shelters, trailer parks, transient housing and other group or nonstandard housing. Completed census forms were due by April 1, 2010 — Census Day — but only 68 percent of forms were received by April 16, compared with 72 percent by that time in 2000 [source: Roberts]. (In the end, 74 percent responded by mail). From May through July, hundreds of thousands of census workers combed the streets to collect data from households that failed to respond by mail.

From July through December, the Census Bureau worked to accurately record and analyze the new population data. By Dec. 31, 2010, the bureau was required by law to report the new Congressional apportionment numbers to the president. The bureau had until April 1, 2011, to provide each state with detailed redistricting data [source: U.S. Census Bureau]. Years later, the bureau's staff of demographers and statisticians continue to examine census data for new revelations into population shifts and trends.

Counting Homeless and Transient People

Census workers count some homeless people in Newark, N.J. during the 1990 census.
Census workers count some homeless people in Newark, N.J. during the 1990 census.
© J A Giordano/CORBIS SABA

According to the Census Bureau, it enlists the help of local experts in finding places where people without housing receive services, such as emergency and transitional shelters, soup kitchens, regularly scheduled mobile food vans and targeted outdoor locations. Census workers go to these locations to conduct the census.

Partnerships with community-based organizations are essential to including migrant and seasonal farm workers in the census. The Census Bureau seeks the advice of local experts to find areas where migrant and seasonal workers live and work, including unregistered labor camps, vehicles parked near work sites and living areas along unnamed roads.

Census takers also interview people staying at campgrounds, fairs and carnivals and marinas. Every person interviewed has the opportunity to report his or her permanent address.

And the bureau works with the Department of Defense and the U.S. Coast Guard to identify living quarters on military installations and ships. All oceangoing, coastal and Great Lake ships take part in what is known as the Census Maritime Enumeration. In addition, the Census Bureau's plan accounts for military personnel and federal civilian government employees, as well as their dependents who are stationed overseas.

When necessary, census takers assist residents who need help in completing the forms. In some facilities, such as jails, the staff distributes census questionnaires. These staff workers, like all census workers, are sworn to protect the confidentiality of the individual.

A complete set of residence rules telling where students, nursing home residents, military personnel and others are counted can be found on the Census Bureau's Web site.

What About Children? Are They Counted?

Census Bureau director Robert Groves meets with Dora the Explorer and families during the launch of "Children Count Too," a program to remind parents to include their young children on the 2010 census form.
Census Bureau director Robert Groves meets with Dora the Explorer and families during the launch of "Children Count Too," a program to remind parents to include their young children on the 2010 census form.
U.S. Census Bureau

While considerable attention has been devoted to the undercount for the U.S. population overall and to specific subgroups such as young, black men in inner cities, less attention has been given to the undercount of children.

In an attempt to fix that problem, the Census Bureau provided hundreds of thousands of Census in Schools kits to every public and private school in America from kindergarten through 12th grade. The kits, which teachers and administrators received in August 2009, provided age-appropriate lesson plans and class materials to teach young people the importance of the census, how maps work, how statistics work, and how the government and private industry use the census figures to improve quality of life for kids, families and communities.

The Census in Schools program provides students with a take-home letter explaining to parents the importance of an accurate census. The letter is available in English, Spanish, Chinese, Vietnamese, Tagalog and Korean. Additional take-home materials provide recreational census activities for students to complete with their parents. The bureau also launched an interactive Web site with census-related games and coloring pages for kids. The Census in Schools program was one of many initiatives to increase census participation and provide the most accurate count possible. As a result, the bureau estimates that it overcounted the entire population by a statistically slim 0.01 percent, down from a 0.49 percent overcount in 2000 [source: El Nasser and Overberg].

What's on the Form?

The 2010 census form had just 10 questions.
The 2010 census form had just 10 questions.
U.S. Census Bureau

During the 2000 census, the Census Bureau mailed out about 83 million short forms (with seven questions) and 15 million long forms (with 52 questions). For the 2010 census, the bureau sent only one form with 10 questions. The 10 questions were designed to collect only the most critical demographic data in the most straightforward way.

The first question on the form asked how many people were living in the household on April 1, 2010. Since respondents sometimes forget to count nonfamily members living in the house, the bureau asked in question two: "Were there any additional people staying here April 1, 2010 that you did not include in Question 1?" As a third safeguard, the 2010 census form then asked respondents to list the names of everyone living in the household.

Each member of the household was asked to answer some basic demographic questions about sex, age, race, Hispanic origin, and relationship to the head of the household. Starting with the 2000 census, respondents were allowed to indicate more than one race. These questions are essential for the federal government to plan for future Social Security and Medicare demands, and to ensure state compliance with antidiscrimination laws like the Civil Rights Act and Voting Rights Act [source: U.S. Census Bureau].

Although there was space on the 2010 form for 12 names, there wasn't room for each person to complete a full list of demographic questions. For households with more than six members, the bureau followed up by phone or in person for additional information.

To ensure the most accurate count, the 2010 census form gave specific instructions about who should and should not be included in the household. For example, if someone was away at college, in prison or in the military on April 1, 2010, he should not have been included as a member of the household. The danger is that he will be counted again at the college, military base or prison.

One reason for the slimmed down census form, is the switch to the American Community Survey for the more in-depth questions. Since 2005, a random sample of Americans has been sent this survey annually. Questions range from type of housing lived in, to income to cost of utilities to education achievement. If you are selected to receive this form, you are required to answer it. The reason for the switch was to provide data that was more current than every 10 years to federal agencies and state governments. Each year 3.5 million addresses are selected [sources: U.S. Census Bureau, Westchester County].

Author's Note: How the Census Works

There is something nostalgic about participating in the census. This thing has been around since the birth of the nation, and it's so strikingly simple — counting people. I love that despite technological upgrades and better marketing, we still have to recruit an army of census workers to go door-to-door counting people without much more than paper and pens. In the age of secret NSA surveillance programs and other government shenanigans, it's understandable that some people question the requirement to provide their personal information to such a large federal agency, but I don't ascribe to the conspiracy theories. I'd rather believe that I'm helping to paint an accurate picture of America at the dawn of the 21st century.

Related Articles


  • Durando, Jessica. "2010 Census Key Dates." USA Today. March 1, 2010. (Aug. 16, 2013)
  • El Nasser, Haya and Copeland, Larry. "Census to cost $1.6 billion less than budgeted." USA Today. Aug. 27, 2010. (Aug. 16, 2013)
  • El Nasser, Haya and Paul Overberg.Census Continues to Undercount Blacks, Hispanics and Kids. USA Today. May 23, 2013. (Aug. 20, 2013)
  • Farley, Robert. "Michele Bachmann claims Constitution only requires you to answer how many people are in your household." June 25, 2009. (Aug.16, 2013)
  • The Leadership Conference. "Census Timeline." (Aug. 16, 2013)
  • Luhby, Tami. "Can GPS make the Census better?" CNN Money. July 1, 2009. (Aug. 16, 2013)
  • Office of the Clerk, U.S. House of Representatives. "Member FAQs: What is the size of the House membership and how is it determined?" (Aug. 16, 2013)
  • Roberts, Sam. "1 in 3 Americans Failed to Return Census Forms." The New York Times. April 16, 2010. (Aug. 16, 2013)
  • Statistics Canada. "North America's First Census." (Aug. 18, 2013)
  • U.S. Census Bureau. "American Community Survey." (Aug. 20, 2013)
  • U.S. Census Bureau. "2010 Census Forms Arrive in 120 Million Mailboxes Across Nation." March 15, 2010. (Aug. 16, 2013)
  • U.S. Census Bureau. "Apportionment Population and Numbers of Representatives, By State: 2010 Census." (Aug. 16, 2010) Population 2010.pdf
  • U.S. Census Bureau. "Center of Population." (Aug. 16, 2013)
  • U.S. Census Bureau. "How It Benefits Your Community." (Aug. 16, 2013)
  • U.S. Census Bureau. "A New Portrait of America, First 2010 Census Results." Dec. 23, 2010. (Aug. 16, 2013)
  • U.S. Census Bureau. "Population Distribution and Change: 2000 to 2010." March 2011. (Aug. 16, 2013)
  • U.S. Census Bureau. "The Questions on the Form." (Aug. 16, 2013)
  • Westchester County. "Census and Statistics." March 12, 2013. (Aug. 24, 2013)