How the Census Works

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].

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].

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:

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

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].

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.

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.

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:

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."