American Community Survey

Intro and Overview

The American Community Survey (ACS) is the largest annual household survey and the only federal survey to include the group quarters (nursing home, dorm, prison etc.) population in the sampling frame aside from the Decennial Census. ACS data are used by policy makers across the country for planning purposes and allocation of funding.

The ACS samples about 3.5 million addresses annually and includes the same topics as the Census plus information about education, employment, internet access, transportation and more. The Public Use Microdata Sample (PUMS) includes about 2/3 of the ACS respondents and is subject to procedures to protect respondent confidentiality like top coding, and omission of more detailed information like birth date or precise geographical location.

The lowest unit of geography in the PUMS is the Public Use Microdata Area (PUMA), which contain at least 100,000 residents. You can access more detailed geography and birth dates in the full count ACS at a Census RDC, like WiscRDC. Beginning with the PUMS is a smart strategy for building to an eventual restricted data project, but many projects are feasible with public use data alone. If you need more detailed geographic information for your project but do not necessarily need microdata, you can consider using the Census published tables for geographies as small as Census block-group Links to an external site.. Step 5 of the Data Dig Activity walks you through how to access these data.

Although the ACS is an annual survey, there are prepared data products that pool across more than one year and allow you to access more detailed information about respondents. For example, using the 5 year ACS PUMS has a higher top-code for income meaning values that would have been topcoded in the 2018 1 year file may not be in the five-year sample. The multi-year files are ideal for studying small populations provided the relationships of interest are expected to be relatively stable over 3-5 adjacent years.

The video describes accessing ACS aggregate data through Data.Census.gov. Step 5 of your Data Dig will walk you through use of the Census API. The link below it takes you to a set of How To videos for IPUMS USA, which is the Integrated Public Use Microdata Series home for ACS and Decennial Census data. This tool allows you to easily and quickly create a data extract containing only the variables you need, for the years and study inclusion criteria you wish to apply, and offers variables that are already harmonized for you.

Closed captioning is available for this video.

IPUMS USA Video Tutorials Links to an external site.

Tips for Getting Started

The ACS is very user friendly. The resources below can help you get started. IPUMS USA (described above) is an excellent resource for a new researcher. Be aware, however, if you plan to eventually pursue a restricted use data project and are using IPUMS that you will need to code up all harmonizations of variables from the original Census variables yourself. IPUMS variables are not available in the RDC. (If you think this applies to you, contact Mary Hamman for some advice).

Key Advantages

Large. Studying small populations and representative estimates of smaller geographic areas is feasible.
Frequent. Surveys are continuously conducted and annual estimates are feasible.
Broad. The ACS includes detailed demographic and socio-economic variables, measures of disability, housing characteristics and much more.
Includes group quarters. For projects that require comparable measures of the group quarters and non-institutional population, the ACS is the best option. However, group quarters data are not representative at levels of geography below state. For this, you will need decennial census data.

Key Disadvantages

Cross-sectional.
Top coding and censoring of detailed geoidentifiers in the PUMS can limit usefulness, but this can be addressed with an eventual restricted use data project.
Comparability. While IPUMS offers many harmonized variables, it's important to read the information under Comparability for each variable you select. Also, there are differences in the sampling frames for the decennial census and the ACS, especially with respect to the group quarters population.
Depth of survey content. While the ACS covers a broad range of topics, the survey instruments for topics like disability or income are not nearly as detailed as the information collected in more specialized surveys.

Papers Using these Data

While there does not appear to be a dedicated bibliography page for the American Community Survey, you can browse the IPUMS Bibliography Links to an external site. entries with Data Collections set to IPUMS USA. This will include both ACS and Decennial Census studies.