ACS 5 year Block Group and Tract Level Data Update

ACS Block Groups and Tracts

ACS Block Groups and Tracts

The information below came from the CTPP Listserve.

The Census Bureau plans to issue a Federal Register notice about the 5-year American Community Survey (ACS) tabulations in August (this month). The 5-year (2005-2009) ACS tabulations are planned to be released around December 2010.

Census 2000 tracts and block groups boundaries are used (not the Census 2010 geography). These ACS tabulations will not have the benefit of the Census 2010 results to be used for sample weighting.

The BLOCK GROUP data from the 5-year American Community Survey (2005-2009):

  • will NOT be available from American Fact Finder;
  • may not be available in the usual “data download” area; and
  • may be restricted to Summary File download and also Data Ferrett.

Ken Hodges of Nielsen said he did not understand why the Census Bureu was applying different data access rules to block group data, when by his estimation, there were many more towns that are smaller than the average block group, and these data access limitations were not being applied to them. The Census Bureau says that block group data should ONLY be used when used to build up larger geographic areas, because the Margins of Error are too large otherwise.

We, the transportation community [CTPP], should be ready to do some small area (tract) analysis when these American Community Survey data are released and then make recommendations as to whether or not to use these 5-year small area tabulations. We know that sub-county estimates, e.g. place and PUMA estimates, have been problematic in some areas.

The Census Bureau is working on web-based tutorials to help data users understand ACS and multiple years of data accumulation and reporting and hopes that they will have materials available in September.

Have you heard of any other interesting ACS developments? If so, please leave a comment.

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