Data Dictionary: ACS 2008 -- 2010 (3-Year Estimates)
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Survey: ACS 2008 -- 2010 (3-Year Estimates)
Data Source: U.S. Census Bureau
Survey Details
ACS 2008 -- 2010 (3-Year Estimates)
Distinguishing features of ACS 1-year, 3-year, and 5-year estimates
1-year estimates 3-year estimates 5-year estimates
12 months of collected data 36 months of collected data 60 months of collected data
Data for areas with populations of 65,000+ Data for areas with populations of 20,000+ Data for all areas
Smallest sample size Larger sample size than 1-year Largest sample size
Less reliable than 3-year or 5-year More reliable than 1-year; less reliable than 5-year Most reliable
Most current data Less current than 1-year estimates; more current than 5-year Least current
Best used when Best used when Best used when

Currency is more important than precision

Analyzing large populations

More precise than 1-year, more current than 5-year

Analyzing smaller populations

Examining smaller geographies because 1-year estimates are not available

Precision is more important than currency

Analyzing very small populations

Examining tracts and other smaller geographies because 1-year estimates are not available

Documentation
ACS 2010 3-Year Summary File: Technical Documentation
Social Explorer; U.S. Census Bureau; American Community Survey 2008-2010 Summary File: Technical Documentation.
Design and Methodology: American Community Survey
Glossary of Terms
Glossary of Basic Geographic and Related Terms - Census 2000
Social Explorer; U.S. Census Bureau; Design and Methodology, American Community Survey. U.S. Government Printing Office, Washington, DC, 2009.