American Community Survey (ACS) Help Guide

Overview of the ACS

Guidance for data users

Practical applications for ACS data

Overview of the ACS

The American Community Survey (ACS) is an ongoing statistical survey of the population in the United States and Puerto Rico.   The U.S. Census Bureau has provided the following important tips for understanding ACS data:

  • The ACS provides us with more detailed population and housing data than the decennial census.  The decennial census describes only basic characteristics of the population such as sex, age, race, Hispanic origin, and homeowner status.  We use the ACS to learn about more detailed demographic, social, economic, and housing characteristics of our population. 
  • ACS data are estimates.  The ACS samples a small percentage of the population every year, unlike the decennial census, which counts the whole population.  Because the ACS data are based on a sample, they are estimates of the actual values for the population. To help users gauge the reliability of the data, the Census Bureau includes a margin of error (MOE) with every ACS estimate.
  • ACS data sets describe either single or multi-year time periods depending on a region's population size.  ACS responses are combined to produce 12 months, 36 months or 60 months of data. These 1-year, 3-year and 5-year data sets contain period estimates, which means they represent the average characteristics of the population and housing in a region during the given data collection period.  The following table describes the availability of ACS period estimates for geographic areas by population size. 


Sample data pooled to produce: Published for areas with:
1-year data sets populations of 65,000 or more
3-year data sets populations of 20,000 or more
5-year data sets populations of almost any size


How to Use ACS Data

Following are just a few of the many resources available to assist users who wish to learn more about ACS data. 

Title Source
Guidance for ACS Data Users U.S. Census Bureau
About the ACS State Data Center of Iowa
Ten Things to Know About the ACS Missouri Census Data Center
Ten More Things to Know (and Do) About the ACS Missouri Census Data Center
Are You Ready for the ACS? Iowa State University
ACS Training Presentations U.S. Census Bureau
How to Use the Census Bureau's American Community Survey Like a Pro
Paul Overberg, USA Today
Census Data in the 21st Century:  Changes and Challenges David Peters, ISU Sociology


Who Uses the ACS?

The U.S. Census Bureau has provided a helpful infographic to describe some practical applications for ACS data.