How the Census Works

By: Dave Roos
Census Protest
Protesters gather outside the U.S. Supreme Court on April 23, 2019 in Washington, D.C. regarding citizenship and the census. On June, 27, 2019, the Supreme Court decided to block that question about U.S. citizenship in the 2020 census. Win McNamee/Getty Images

There's an old-school beauty to the United States census. Every 10 years since 1790, the country takes a national headcount. That first census, required by the U.S. Constitution and instituted by President George Washington, counted fewer than 4 million people. The most recent census, in 2010, recorded 308.7 million men, women and children of dazzling diversity. The process of taking the census has changed — from house-to-house census takers to online questionnaires — but the mission remains the same, to paint an accurate picture of the changing face of America.

The main purpose of the census is to figure out how many seats each state receives in the U.S. 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. 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 $675 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.

So how did the census come into being?


History of the Census

1800 Census
The 1800 census included 16 states and territories. The ages of free white males and females were recorded in several age categories. Indians, slaves, and free blacks were not divided into age groups. U.S. Census Bureau

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 [source: Merry]. 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.


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 House of Representatives. In 1790, George Washington signed the act into law [source: U.S. Census Bureau]. 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 guide "Finding Treasure 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 2020 census, which is projected to cost $15.6 billion or close to $100 per U.S. household [source: GAO].


Technology and the Census

punch cards, 1940 census
Census Bureau employees review punch cards containing data from the 1940 census. 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 [source: U.S. Census Bureau]. 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 completed 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. This was the first successfully used civilian computer. Data was input using magnetic tape as well as via punch cards. That technology has advanced over the years and now high-speed supercomputers assist with the census [source: U.S. Census Bureau].


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 correctly 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 0.5 percent error rate [source: Luhby].

The biggest technological upgrade for 2020 is that it will be the very first census that can be completed online. Most U.S. households received a mailed invitation in March 2020 to go online and complete the census. Only households that fail to complete the census by early April will receive a paper questionnaire [source: U.S. Census Bureau]. The hope is that the online census will improve response rates and lower the cost of sending census workers to follow up.

Another cost-cutting technology debuting in 2020 is the use of satellite imagery to locate new homes and identify those that no longer exist. In the past, census workers had to physically canvas all urban rural locations to verify addresses. Now many of the farthest-flung locations can be checked remotely by comparing old and new satellite images. The move to satellite verification is expected to reduce the canvassing workforce from 150,000 workers in 2010 to only 60,000 in 2020 [source: CBS News].

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 [source: U.S. Census Bureau].


Why Is the Census Important?

Indians, 1910 Census
A census enumerator interviews Winnebago Indians in Wisconsin in 1910. 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 $675 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:

  • Census numbers help communities work out strategies to deal with traffic congestion or overcrowded schools. Nonprofit organizations use census numbers to estimate the number of potential volunteers in communities across the nation.
  • 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.
  • Census numbers help industry reduce financial risk and locate potential markets. This means that businesses can determine the marketability of potential products.
  • It helps with genealogy research. 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, American children may be using past census information to do their homework.)


Privacy and Security of Census Data

By law, the Census Bureau cannot share census answers with other government agencies, including welfare agencies, immigration, the police or FBI, the Internal Revenue Service, courts or 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 or $250,000 in fines or both [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 [source: U.S. Census Bureau]. This is to protect personally identifiable information from going public. The rationale is that little negative impact could happen after 72 years, since most of the people listed would be gone or were young children when it was collected. 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 complete 1950 census records will be released in April 2022 [source: U.S. Census Bureau].

How Does the Census Process Actually Work?

1980 Census
During the 1980 census, most people received and replied to the census by mail, a practice that started in 1960. Door-to-door visits still continue for hard-to-reach populations. U.S. Census Bureau

Collecting and reporting census data is a multiyear process. The 2020 census actually began back in March 2018, when the bureau officially submitted its 2020 census questions to the United States Congress [source U.S. Census Bureau]. The new batch of eight questions included one about citizenship, which hasn't been asked in any form since 1950. That citizenship question was challenged and the Supreme Court has ruled against it (see sidebar), though President Trump threatened to delay the Census because of this [source: CNN].

Census workers were also hired throughout 2018 and 2019 to begin the work of canvassing neighborhoods — both online using satellite images and in person — to verify addresses. During the summer of 2019, state governments will also be tasked with providing the Census Bureau with the locations of all known "transitory" housing locations, such as RV parks, campgrounds, carnivals, and long-term stay hotels and motels.


Data collection for the 2020 census began in earnest on Jan. 21, 2020, when census workers traveled by bush plane and snowmobile to reach Toksook Bay, Alaska, estimated population 661 [source: U.S. Census Bureau, Wang]. 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].

The rest of the country received their first census invitation in mid-to-late March 2020 (March 12-20). For 95 percent of households, the first invitation will come in the mail, but it won't include a paper census questionnaire. Instead, households are directed to a web address to complete the census online. The delivery is staggered so as to space out the numbers of recipients going online to fill out the census form. For the 2020 census, paper questionnaires will only be delivered to households that don't receive mail at a physical location (people who get their mail in a P.O. box, for example, or people affected by a natural disaster) [source: U.S. Census Bureau]. Those paper questionnaires will be delivered directly by census workers.

Completed census forms will officially be due on April 1, 2020 — Census Day. Normally, from May through July, hundreds of thousands of census workers comb the streets to collect data from households that failed to respond by mail. However, due to the coronavirus pandemic, these operations will be delayed. In 2010, only 68 percent of forms were received by April 16 [source: Roberts]. In the end, 74 percent responded by mail.

The Census Bureau will also conduct 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.

From July through December, the Census Bureau will crunch numbers to accurately record and analyze the new population data. By Dec. 31, 2020, the bureau is required by law to report the new Congressional apportionment numbers to the president. The bureau will have until April 1, 2021, to provide each state with detailed redistricting data [source: U.S. Census Bureau]. Both of these dates could be pushed back depending on the severity of the delays due to the coronavirus pandemic.


Counting Homeless and Transient People

counting homeless, Los Angeles
Volunteers count homeless people during the 2015 Greater Los Angeles Homeless Count. Census workers also try to count the homeless and other transient people with the help of local experts. U.S. Census Bureau

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 then visit these locations personally 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.


What's on the 2020 Census Form?

There used to be two census questionnaires, known as the "short-form" and the "long-form" questionnaire. From 1970 through 2000, most households received the shorter version, which primarily asked questions about the number of people living in the household and their characteristics (age, sex, race, etc.). A smaller random sample received the longer version, which included detailed demographic and economic data (52 total questions). Starting with the 2010 census, everyone gets just the shorter form, which has 10 to 12 questions. The long-form questionnaire was replaced with the American Community Survey, a detailed questionnaire randomly sent to 3.5 million American households every year (not just once a decade) that provides up-to-the-minute demographic data in between census years.

So what are the exact questions on the 2020 census? Here are the questions:


  1. "How many people were living or staying in this house, apartment or mobile home on April 1, 2020?" This question seems straightforward, but often causes the most confusion. As the form will explain in its instructions, households should only count the number of people currently living or staying in the home, not family members who are currently living elsewhere (college, military, prison, nursing home, etc.) Also, there could be people living in the home who aren't immediate family (nephew, boyfriend, paid boarder) but should be included in this count.
  2. "Were there any additional people staying here April 1, 2020 that you did not include in Question 1?" This is a safeguard to double-check that households didn't leave out people that should have been counted.
  3. "Is this house, apartment or mobile home..." Owned, rented, or occupied without payment of any kind? And if it's owned, do you have a mortgage? This question, asked since 1890, helps the government know if there's enough housing for everyone across all demographics.
  4. "What's your telephone number?" In case they need to call to clarify an answer.
  5. "What is Person 1's name?" "Person 1" is the individual who owns or rents the house. The questionnaire starts with a series of questions about the characteristics of Person 1, namely:
  6. "What is this person's sex?" For 2020, there are still only two possible answers for this question: male or female.
  7. "What is this person's age and what is their date of birth?" The age question is asked in two different ways to improve accuracy.
  8. "Is this person Hispanic, Latino, or Spanish origin?" Since 1970, the census has asked about Hispanic origin separate from race, since people of Hispanic or Latino origin can be of many different races: white, black, Native American, etc. There was a proposal to combine the race and Hispanic origin questions into one category as it has caused confusion among responders in the past. Since that change was not approved, the census question remains as it was before.
  9. "What is this person's race?" Racial statistics are used to ensure that government-funded programs serve all Americans equally and fairly. There are 14 racial designations, plus room to write in more specific answers, such as a particular Native American tribe. This year for the first time, if a person selects the "white" or "black" categories they get to indicate their ethnic origins, such as "German," "Lebanese," "African American," "Jamaican," etc. There are also check boxes to specify country of origin if a person checks Asian/Pacific Islander such as "Vietnamese, "Samoan," etc.
  10. Print the name of Person 2: After Person 1 is done, the rest of the people in the household are asked the same batch of questions plus the following:

Does this person sometimes live or stay somewhere else? If the answer is "yes," the respondent can check a box for college, prison, military service, or with another relative, among other options.

"How is this person related to Person 1?" For the first time in 2020, there is an option to register same-sex relationships. Instead of choosing simply "husband or wife," which was how the 2010 census framed it, respondents to the 2020 census can choose either "Opposite-sex husband/wife/spouse" or "Same-sex husband/wife/spouse" in addition to "Opposite-sex unmarried partner" and "Same-sex unmarried partner."


Lots More Information

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)
  • Green, Judy Hanna, "U.S. Census Background." Finding Treasure in the U.S. Census Federal Census. (April 26, 2019)
  • The Leadership Conference. "Census Timeline." (Aug. 16, 2013)
  • Liptak, Adam. "The Supreme Court Will Soon Consider Whether the Census Will Include a Citizenship Question." The New York Times. April 15, 2019 (April 26, 2019)
  • 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)
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  • U.S. Census Bureau. "How It Benefits Your Community." (Aug. 16, 2013)
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