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American Community Survey

Census.govAmerican Community Survey › Guidance for Data Users: When to use 1-year, 3-year, or 5-year estimates
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When to use 1-year, 3-year, or 5-year estimates

Choosing which dataset involves more than simply considering the population size in your area. You must think about the balance between currency and sample size/reliability/precision.

For details, research implications, and examples, see "Understanding and Using ACS Single-Year and Multiyear Estimates," page 9 in General Data Users Handbook [PDF 1.6MB]

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


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Source: U.S. Census Bureau | American Community Survey Office | Email ACS | Last Revised: June 27, 2014
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