Overview

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Census tract geodemographics are used for wide ranging reporting, research and analysis applications. This document reviews how you can access and use these data. Census tract data are used to determine eligibility and application for participation in Federal, state, and local government programs. Many Federal compliance reporting programs require the census tract geocode be reported for addresses served by or participating in regulated activities. Census tracts are defined by the Census Bureau and organized as sub-county building blocks. While the Census Bureau is the primary source for public use demographic data tabulated for census tract areas, many organizations tabulate their own data for census tract geography.

Reasons for widespread use of census tract demographics result in part from the more extensive scope of subject matter available from the decennial census for census tracts than for other smaller area geographic tabulation levels (such as census blocks and block groups). Census tracts are small, designed to average 4,000 population, but census tract estimates have a relatively smaller estimation error than do smaller geographic areas such as block groups. The approximate 65,000 census tracts covering the U.S. wall-to-wall provide a good geographic granularity to meet many needs.

Unchanging throughout the decade, census tract and census block group (census tract subdivisions) boundaries are subject to update for each decennial census. Many census tract and block group boundaries will remain unchanged for Census 2010. See the Census 2010 census tract and block group final criteria descriptions. See the About Census Tracts section for more information about definition and structure.

Applications reviewed here are focused on Census 2000 population, households, families and income. Thousands of additional subject matter items are available from Census 2000. Ongoing census tract quarterly updates are developed by Proximity (see Quarterly Census Tract Estimates). In December 2010, census tract updates will become available from the Census Bureau American Community Survey (ACS) "5-year rolling estimates" -- tabulations for the ACS coverage period 2005-09. In mid-2011, complete count census tract data will become available from Census 2010. There will be no census tract sample-based estimates (as available from Census 2000 and previous decennial censuses). See more about ACS and Census 2010. See examples of GIS applications making use of census tracts and linking these with other geographies at http://proximityone.com/gallery/guide.

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