Census Data Resources: Understanding the Data

Guide to (mostly online) resources for manipulating and extracting Census data.

About the Surveys

The American Community Survey (ACS) replaced the decennial long form beginning in 2005.  While the subjects are very similar between the ACS and the decennial long form, the survey methodology is substantially different.  Variables, even with the same name, may not be comparable between the two surveys.

Read more about the American Community Survey.

Read more about the Decennial Census.

Maki images courtesy of Mapbox

Questions Asked and Subjects Included in the Decennial Censuses and the ACS

How to Choose a Census Tool

  • What year do you need?

American FactFinder has only the most recent years of its surveys; Social Explorer and NHGIS have all the population ones back to the first one in 1790.

  • What geography do you need?

American FactFinder has ALL available geographies (except block groups for ACS data prior to 2013); Social Explorer and NHGIS have block groups for all ACS years.  NHGIS has all geographies.  Social Explorer may not have some less common geographies.

  • Which variable(s) do you need?

American FactFinder has all available variables; Social Explorer doesn’t have variables that involve some suppression.  NHGIS is working to include all but is a work in progress.

  • Do you need to make a map without using GIS?

Social Explorer and American FactFinder both have this capability; American FactFinder is harder but has some variables (from current surveys!) that Social Explorer does not.

  • Do you need to make a map with GIS?

Only NHGIS allows download of shapefiles for use with ESRI mapping products.

  • Do you need microdata?

Only DataFerrett or IPUMS* provide access to public use microdata sample (PUMS) data (but the only available geographies are public use microdata areas [PUMAs], super-PUMAs or higher levels of geography, e.g., states).

  • Are the pre-fabricated tables sufficient or do you need to create your own?

Only DataFerrett* allows you to create your own, but only with PUMS data, so only with PUMS geographies.

  • What survey do you need?

American FactFinder has most of the (current) Bureau surveys; Social Explorer has all of the decennial population surveys, 1790 to present plus a few other things; DataFerrett* has decennial and ACS data, the Current Population Survey and a few other Bureau surveys (SIPP, SAIPE, et al.), plus non-Bureau data like the Home Mortgage Disclosure Act data; the National Survey of Fishing, Hunting and Wildlife-Associated Recreation; and much more.

  • How precise do you need to be?

Social Explorer doesn’t provide margins of error (MOEs) with the data.  If you need to be extremely precise, get data from NHGIS or AFF to be able to evaluate the MOEs.

*If you need help, see contact information above at right for the Librarian for Numeric Data Services and Data Management.


ACS Documentation

Decennial Documentation


Michele Hayslett

Data Management
Numeric Data
Census Data
Locating Data
Website / Blog Page
  • Last Updated: Nov 17, 2015 12:17 PM
  • URL: http://guides.lib.unc.edu/census