This webpage and accompanying materials document the process to create master index files capable of linking various U.S. Census Bureau (Census) data products. Systematically linking various datasets together will allow Census data users to assemble information for statistical and geographic analysis.
Why create Master Index Files?
The Census makes available to the public vast datasets containing extremely detailed and valuable population and demographic data, for example:
- 2010 Decennial Census Summary File 1 (Census SF1)
- 2006-2010 American Community Survey (ACS) Five Year Estimates
- 2007-2011 ACS Five Year Estimates
The Census also generates and provides geographic files compatible with software packages, examples of TIGER/Line shapefiles are:
- Census Tracts (Tract)
- Census Block Group (Block Group)
- Census Block (Block)
The data for each of the six Census products above contain identification fields. In some cases, the ID fields are similar and therefore capable of acting as a link between datasets However, in many cases the Census data products do not contain one unifying field capable of a clean, reliable link between large datasets.
How do the Master Index Files work?
Each index file contains record identifier numbers from 2010 Census SF1, 2006-2010 ACS, and 2007-2011 ACS and FIPS location codes Tracts, Block Groups, and Block geographies for each of the 50 states, plus Washington DC and the territory of Puerto Rico. The files are compatible with many types of software: Microsoft Excel, Microsoft Access, SAS, SPSS, ArcGIS, and etcetera. The key files act as the relational link between disparate datasets. There is a key index file for each state, Washington DC, and Puerto Rico. Each key file is itself a comma-delimited text file. The files are available to the public by state in compressed folders containing the key file and supporting materials (see below).
NOTE: the master index files do not contain population or demographic data of any sort. The files do contain several ID fields so that users can link SF1 and ACS data to each other and to Census TigerLine Geographic products; and possibly other datasets with similar ID fields.Visit the following webpages to obtain U.S. Census summary file datasets:
- Download SF1 Datasets: http://www2.census.gov/census_2010/04-Summary_File_1/
- Download SF2 Datasets: http://www2.census.gov/census_2010/05-Summary_File_2/
Documentation and Background Materials
“Census-ACS Master Index Files: Documentation and User’s Guide” provides background information about the development, testing, and use of the master index files. The master index files are an iterative product meshing existing datasets and documentation into one index. As such, the authors referenced many documents related to the 2010 Decennial Census and American Community Survey. All of the files and data used to create the master index files are in the public domain and available online. Please refer to the documentation report (linked to in paragraph above) or download the two files below for more information.
American Community Survey Resources (reference materials and tools in compressed folder)
Decennial Census Resources (reference materials and tools in compressed folder)
The key index files are the result of a voluntary effort of Dr. Michael Greenwald (personal) and Jonathan Brooks (Texas A&M Transportation Institute). Texas A&M Transportation Institute is voluntarily providing a home to the files and is in no way responsible for the accuracy of or use of the files. In exchange for providing these data archives in the public domain, the user understands and agrees that:
- They use these data sets at their own risk. While all reasonable efforts have been made to ensure the validity of these index file data sets, no warranty of any kind is either expressed or implied. User is strongly encouraged to perform their own data validity checks to ensure the index files are returning reasonable results;
- User’s rights are non-exclusive. Use of these archives by other individuals or organizations in no way infringes on the rights of the user. Neither does the user have any cause to interfere with the use of these archives by other individuals or organizations;
- For-profit redistribution of this agreement, the technical documentation and any of the data archives, whether in full or partial, without express prior written consent is prohibited;
- Periodic updates to these archives and documentation may be made to these archives to address data errors or expand functionality. Any such updates are understood to happen on an ad hoc basis, without advance notice. An update shall not create or imply liability for errors or omissions identified in any previous versions.
In the event an error or data abnormality is noticed, please notify Dr. Michael J. Greenwald via e-mail ([email protected]), as soon as possible. Your e-mail should contain enough detail for Dr. Greenwald to document and identify the problem. Dr. Greenwald will respond as time constraints allow.
Download Master Index Files
There is a key index file for each state, Washington DC, and Puerto Rico. Each key file is itself a comma-delimited text file. The files are available to the public by state in compressed folders containing the key file and supporting materials (see below). Please be aware that the downloadable files linked below range in size from 2mb to 138mb – and consequently may take one or two minutes to download. Click on a state name to download the file. Or, click on the link at the top of the list to download the entire set (a compressed folder containing a folder for each state and documentation) – WARNING – this file is approximately 1.7 gigabytes (1,700mb) and may not successfully download using some internet browsers.
Full Set of Master Index Files (warning – file is approximately 1.7 gigabytes)