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

How Does the Census Process Actually Work?

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.