For the 2012 ACS data release, there are tract numbering corrections to seven census tracts in Pima County, Arizona. In addition, one deleted census tract is restored in Los Angeles County, California, eliminating one 2010 tract and changing the geographic definition of another census tract involved.

Pima County, Arizona

The numbering of the seven census tracts below in Pima County changed, but their geographic definitions remain the same as their 2010 census tract definitions.

Census Tract 27.01 is now 27.04
Census Tract 29.03 is now 29.06
Census Tract 4105.01 is now 41.18
Census Tract 4105.02 is now 41.21
Census Tract 4105.03 is now 41.25
Census Tract 4704.00 is now 52.00
Census Tract 4705.00 is now 53.00

Los Angeles County, California

The deletion of Census 2000 Tract 1370.00 is now corrected, and the tract is reinstated with its former boundaries. This change incorporates all of former (2010) Census Tract 9304.01 and part of (2010) Census Tract 8002.04 into the reinstated (2012) tract 1370.00.

For additional details on these tract and related changes, please see 2010 Census Geography Notes [PDF - <1.0 MB].

The 2012 ACS estimates are the first to include tabulations for the new 2010 Public Use Microdata Areas (PUMAs). The 2010 PUMAs were defined using the results of the 2010 Census.

2010 PUMAs:

• Nest within states or equivalent entities
• Cover the entirety of the United States, Puerto Rico, and the Island Areas that contain a 2010 Census population of 100,000 or more
• Are built on counties and census tracts PUMA delineations are subject to population thresholds and building block geography
• Must be geographically contiguous (unless the geographical features of the county or census tract used as a building block are noncontiguous, i.e., islands, offshore features)
• Some 2010 PUMAs include descriptive names, as designated by local participants

For additional details, please see Public Use Microdata Areas (PUMAs).

The 2012 ACS estimates are the first to include tabulations for the 2010 Census Urban Area definitions and Urban/Rural classification.

The Census Bureau’s urban-rural classification is fundamentally a delineation of geographical areas, identifying both individual urban areas and the rural areas of the nation. The Census Bureau’s urban areas represent densely developed territory, and encompass residential, commercial, and other non-residential urban land uses.

For the 2010 Census, an urban area will comprise a densely settled core of census tracts and/or census blocks that meet minimum population density requirements, along with adjacent territory containing non-residential urban land uses as well as territory with low population density included to link outlying densely settled territory with the densely settled core. To qualify as an urban area, the territory identified according to criteria must encompass at least 2,500 people, at least 1,500 of which reside outside institutional group quarters. The Census Bureau identifies two types of urban areas:

• Urbanized Areas (UAs) of 50,000 or more people;
• Urban Clusters (UCs) of at least 2,500 and less than 50,000 people.

“Rural” encompasses all population, housing, and territory not included within an urban area.

For additional details, please see 2010 Census Urban and Rural Classification and Urban Area Criteria.