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1-year and 3-year ACS estimates

In 2008 two types of estimates are available from the American Community Survey: one-year estimates (based on data collected in a single year) and three-year estimates (based on data collected in three consecutive years). To help users determine which estimates to select, a basic comparison of one-year and three-year estimates is provided below. Additional information about the interpretation and use of one-year and three-year estimates is available on the ACS website.


One-Year Estimates

The 2007 ACS one-year estimates are based on data collected between January 2007 and December 2007.

  • Published for selected geographic areas with populations of 65,000 or greater
  • Represent the average characteristics over calendar year 2007
  • Have smaller sample size than the three-year estimates
  • Are more current than the three-year estimates



Three-Year Estimates

The 2005-2007 ACS three-year estimates are based on data collected between January 2005 and December 2007.

  • Published for selected geographic areas with populations of 20,000 or greater
  • Represent the average characteristics over the 3-year period of time
  • Have larger sample size than the one-year estimates
  • Are less current than the one-year estimates


For areas with a population less than 20,000, five-year estimates will be available. The first five-year estimates based on ACS data collected from 2005 through 2009 will be released in 2010.



Source: U.S. Census Bureau.   Last Revised: August 26, 2008

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