Understanding Single-Year and Multi-Year Estimates
The ACS provides several advantages over the information that has been collected in the past through the decennial census long-form samples. The main benefits of the ACS are timeliness and access to annual data for states and local areas with larger populations, by using single-year estimates. Multi-year estimates are used to provide data for areas with smaller populations.
Currently, single-year estimates are published for areas with 65,000 or more residents, and three-year estimates are published for areas with 20,000 or more residents. Beginning in 2010, five-year estimates will be published for areas with fewer than 20,000 residents. While a single-year estimate includes information collected over a 12-month period, a 3-year estimate represents data collected over a 36-month period, and a 5-year estimate includes data collected over a 60month period. The primary advantage of using multiyear estimates is the increased statistical reliability of the data for less populated areas and small population subgroups. For these less populated areas and groups, the level of precision improves dramatically with the three-year and five-year estimates.
Release Schedule for ACS Data
| Data Product | Population Threshold | Year of Data Release | |||||||
|---|---|---|---|---|---|---|---|---|---|
| 2006 | 2007 | 2008 | 2009 | 2009 | 2010 | 2012 | 2013 | ||
| Year(s) data was collected | |||||||||
| 1-year estimates | 65,000+ | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 |
| 3-year estimates | 20,000+ | 2005-2007 | 2006-2008 | 2007-2009 | 2008-2010 | 2009-2011 | 2010-2012 | ||
| 5-year estimates | Census block groups and larger | 2005-2009 | 2006-2010 | 2007-2011 | 2008-2012 | ||||
Source: U.S. Census Bureau, A Compass for Understanding and Using American Community Survey Data: What General Data Users Need to Know,U.S. Government Printing Office, Washington, DC, 2008, p.3, Table 2.