Peter J Wilcoxen > PAI 789 Advanced Policy Analysis

Census Documentation

Selected information useful in working with Census data

API Information

Census API List
A comprehensive list of the datasets available.
Signup Page for a Census API Key
Get your own API key here.

Geographic Entities

Hierarchy of Census Geographic Entities
Diagram showing how larger geographic areas are linked to smaller ones.
Relationships Between Smaller Geographic Entities
Diagrams showing how counties, tracts, block groups and blocks are related.
Understanding Census GEOIDs
Shows how GEOIDs are defined for states, counties, tracts, and other entities.

Finding Data in the ACS

If you need data that's probably in the ACS but you're not sure where to find it, look through the links below. Use the first link to figure out roughly where the tables are that cover the topic; then use the second link to see if there are specific tables that may work; and then use the third link to figure out the individual variable IDs. Note that some of this information is for the 2019 ACS because the 2020 was just becoming available during the spring of 2022. If you need to use the 2020 data, check that documentation to be sure the variable IDs have not changed.

  1. Guide to Table IDs
  2. See "Element 2" for a list of major topic areas and the corresponding table ID codes.
  3. Detailed List of Tables
  4. An Excel file has a detailed list of tables, but not individual variables. It's a good second step after looking at the subject list.
  5. Detailed List of Table Shells
  6. An Excel file with a listing of every variable in every table. The place to go when you need the ID of a specific variable.

Public Use Microdata Sample (PUMS)

The PUMS data is a sample of the records from individuals and households that underly the ACS. The data is available down to the state level but is not available for counties, tracts or block groups. Instead there is a sub-state level know as Public Use Microdata Areas (PUMAs), which typically have around 100,000 residents.

Main Documentation Page for the ACS PUMS Data
A description of the PUMS data.
ACS 5-Year PUMS API Documentation
Instructions on how to use the PUMS API.
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Peter J Wilcoxen, The Maxwell School, Syracuse University
Revised 03/20/2024