How the American Community Survey Works

(April 2009) The American Community Survey (ACS) samples nearly 3 million addresses each year, resulting in nearly 2 million final interviews. The annual ACS sample is much smaller than that of the Census 2000 long-form sample, which included about 18 million housing units. As a result, the ACS needs to combine population or housing data from multiple years to produce reliable numbers for small counties, neighborhoods, and other local areas. To provide information for communities each year, the ACS will provide one-year, three-year, and five-year estimates of data.

ACS data are very timely because they are released in the year immediately following the year in which they are collected. ACS data collected from 2000 through 2004, and published from 2001 through 2005, are available for geographic areas with 250,000 people or more, including all states, the District of Columbia, and many large counties and cities. As shown in the table, starting with the data collected in 2005, ACS information has been published for areas with populations of 65,000 or more. In December 2008, the first three-year estimates were released based on data from the 2005, 2006, and 2007 surveys. By December 2009 the ACS will have sampled approximately 15 million addresses, and by 2010, the ACS will provide the first five-year estimates of demographic, housing, social and economic data for the nation, states, cities, counties, and other small geographic areas. These five-year estimates will then be updated annually by removing the earliest year and replacing it with the latest one and will provide, for the first time, the ability to monitor social and economic trends in local communities.