What is the American Community Survey (ACS)?

The American Community Survey (ACS) differs from the decennial census in that it provides a period estimate rather than a point-in-time estimate. For example, the 2020 Census “long form” sampled the population on April 1st, 2020 and is considered a point-in-time estimate, since the data was acquired in a day. Conversely, ACS data is acquired over a period of time. The two most commonly used ACS estimates are the 1-year estimates and the 5-year estimates. The 1-year estimates are collected over a 12-month period, while the 5-year estimates are collected over a 60-month period. More information on the difference ACS surveys can be found in the table below.

1-year estimates	1-year supplemental estimates	3-year estimates*	5-year estimates
12 months of collected data Example: 2022 ACS 1-year estimates Date collected between: January 1, 2022 and December 31, 2022	12 months of collected data Example: 2022 ACS 1-year supplemental estimates Date collected between: January 1, 2022 and December 31, 2022	36 months of collected data Example: 2011-2013 ACS 3-year estimates Date collected between: January 1, 2011 and December 31, 2013	60 months of collected data Example: 2018-2022 ACS 5-year estimates Date collected between: January 1, 2018 and December 31, 2022
Data for areas with populations of 65,000+	Data for areas with populations of 20,000+	Data for areas with populations of 20,000+	Data for all areas
Smallest sample size	Smallest sample size	Larger sample size than 1-year	Largest sample size
Less reliable than 3-year or 5-year	Less reliable than 5-year	More reliable than 1-year; less reliable than 5-year	Most reliable
Most current data	Most current data	Less current than 1-year estimates; more current than 5-year	Least current
Annually released: 2005-present	Annually released: 2014-present	Annually released: 2007-2013	Annually released: 2009-present
Best used when	Best used when	Best used when	Best used when
Currency is more important than precision Analyzing large populations	Currency is more important than precision Analyzing smaller populations Examining smaller geographies because the standard 1-year estimates are not available	More precise than 1-year, spans fewer years than 5-year Analyzing smaller populations Examining smaller geographies because the standard 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

Source: US Census Bureau

*ACS 3-year estimates have been discontinued. The 2005-2007, 2006-2008, 2007-2009, 2008-2010, 2009-2011, 2010-2012 and 2011-2013 ACS 3-year estimates will remain available to data users, but no new 3-year estimates will be produced. Every community in the nation will continue to receive a detailed statistical portrait of its social, economic, housing and demographic characteristics through 1-year and 5-year ACS products.

Margin of Error

Since the ACS data are estimates and not exact counts of the entire population, the US Census Bureau establishes a margin of error (MOE) for each estimate. The margin of error (MOE) can be used to create ranges for all ACS estimates and are at the 90% confidence level.

ACS Helpful Hints

When discussing the multi-year period estimates, the best way to characterize the data is to state that the data cover a period of years, rather than use the year of release. For example, for a 5-year estimate, released in 2022 the data might be characterized as, “The poverty rate in this community over the period 2018-2022 was X percent”.
If comparisons are to be made between various communities, care should be taken to ensure that the same period estimates are used; 1-year data should only be compared with other 1-year data; 3-year data compared only with other 3-year data and 5-year data with other 5-year data. With the 3- and 5-year multi-year estimates, time series comparisons should only be done with non-overlapping data; for example the 5-year estimate for 2012-17 can be compared to the 2018-22 5-year estimates.