The U.S. Census counts every resident in the United States. It is mandated by Article I, Section 2 of the Constitution and takes place every 10 years. The data collected by the decennial census determine the number of seats each state has in the U.S. House of Representatives and is also used to distribute billions in federal funds to local communities. Additional Information can be found at Through the Decades.
Over the years, Congress has authorized additional questions, enabling us to better understand the nation's inhabitants and their activities and needs. Through the decades, the census has collected data on race, ancestry, education, health, housing, and transportation. An examination of the questions asked during each census illustrates changes in our nation's understanding of race, the impact of immigration, growth of the Hispanic population, and computer usage. Visit the web site: Index of Questions for lists of the questions asked during each census.
Between 1970 and 2000, the U.S. Census Bureau used two questionnaires. Most households received a short-form questionnaire asking a minimum number of questions. A sample of households received a long-form questionnaire that included additional questions about the household.
The 2010 Census had just one questionnaire consisting of ten questions. (Read more about Questionnaires from 1790 to 2010.)
Launched in 2005, the American Community Survey (ACS) is part of the decennial census program and is essentially what used to be the long form.
ACS data are collected continuously throughout the year and throughout the decade from a relatively small sample of the population (3 million addresses annually). During the decennial census program, about 250,000 households a month will receive both the ACS and the 2010 Census form. The ACS collects detailed information on the characteristics of population and housing on an ongoing basis. These data were previously collected only in census years in conjunction with the decennial census.
During Census 2000, the Census Bureau asked for this detailed information from one in every six addresses. The ACS questionnaire collects nearly the same information and is sent to approximately the same number of addresses over a five-year period. However, since the ACS is conducted every year, rather than once every 10 years, it provides more current data throughout the decade.
Like the 2010 Census participation in the ACS is mandatory by law and the American public’s participation is vital to provide data that impacts policy decisions on the local, state, and federal level.
For more information, read: When to use 1-year, 3-year, or 5-year estimates