The American Community Survey (ACS) is an ongoing survey conducted by the U.S. Census Bureau since 2005. In 2010, the ACS replaced the decennial census long form as the source of sample data for population and housing indicators. The short form of the decennial census is still distributed to obtain a count of the entire U.S. population.

ACS asks questions about age, sex, race, family and relationships, income and benefits, health insurance, education, veteran status, disabilities, employment location and mode of travel to work, place of residence, price paid for living essentials. You can review the annual questionnaires to see the precise questions asked each year. For side-by-side comparisons of ACS questionnaires, visit the ACS Questionnaire Changes page. 

There are both benefits and challenges associated with replacing the long form with ACS. The primary benefit is the freshness of data: ACS data is collected every year, whereas the decennial census was collected every ten years. Challenges include a higher sampling error for the ACS, due to a smaller sample population, and difficulties comparing data from year to year.

Each year, the Census Bureau releases 1-, 3- and 5-year estimates based on information gathered in the ACS. Important note: if you wish to compare ACS estimates to earlier Decennial Census data, please review these cautions first.

In deciding which estimate you want to use, you should consider the currency of data; the geographic size of your population; and the acceptable sample size/reliability of the data. The Census Bureau chart below shows distinguishing features of the different estimates.

This guide is adapted from UC San Diego's Census Research Guide by Kelly L. Smith.