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Decennial Census P.L. 94-171 Redistricting Data

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P.L. 94-171 Redistricting Data

Public Law (P.L.) 94-171, enacted by Congress in December 1975, requires the Census Bureau to provide states the opportunity to identify the small area geography for which they need data in order to conduct legislative redistricting. The law also requires the U.S. Census Bureau to furnish tabulations of population to each state, including for those small areas the states have identified, within one year of Census day.

Since the first Census Redistricting Data Program, conducted as part of the 1980 census, the U.S. Census Bureau has included summaries for the major race groups specified by the Statistical Programs and Standards Office of the U.S. Office of Management and Budget (OMB) in Directive 15 (as issued in 1977 and revised in 1997). Originally, the tabulation groups included White, Black, American Indian/Alaska Native, and Asian/Pacific Islander, plus “some other race.” These race data were also cross-tabulated by Hispanic/Non-Hispanic origin. At the request of the state legislatures and the Department of Justice, for the 1990 Census Redistricting Data Program, voting age (18 years old and over) was added to the cross-tabulation of race and Hispanic origin. For the 2000 Census, these categories were revised to the current categories used today.

2010
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2010

2010 Census (P.L. 94-171) Redistricting Data Summary Files

The 2010 Census (P.L. 94-171) Redistricting Data Summary Files were posted, by state, from February 3rd through March 24th of 2011. These summary file tables contain tabulations for:

  • Table P1 - Race
  • Table P2 - Hispanic or Latino, and not Hispanic or Latino by Race
  • Table P3 - Race for the Population 18 Years and Over
  • Table P4 - Hispanic or Latino, and not Hispanic or Latino by Race for the Population 18 Years and Over
  • Table H1 - Occupancy Status (Housing)

The 2010 Census (P.L. 94-171) Redistricting Data Summary File data are available for all 50 states, the District of Columbia, and Puerto Rico through data.census.gov and via FTP download.

Technical support for use of the FTP summary files in the form of technical documentation, which includes records layouts, are available as PDF documents. In addition, SAS, Microsoft Access shells and instructions for using the traditional Decennial summary file format are provided. These materials are all provided below.

The 2010 Census (P.L. 94-171) Redistricting Data Summary File Technical Documentation is available in English, and in Spanish specifically for Puerto Rico.

Using Microsoft Access to extract data from the 2010 Census (P.L. 94-171) Redistricting Data Summary Files

Using file transfer protocols (FTP) for accessing and importing the 2010 Census (P.L. 94-171) Redistricting Data Summary File data using the Access 2003 shell or the Access 2007 shell.

  • How to use the provided MS Access shells to import and extract the summary file data.
  • NOTE: In some large states, the combined size of the data tables may exceed the size limitation of Access. This can be overcome by using multiple Access databases and then linking the tables from each of the databases. Please contact 301-763-4039 should you encounter this problem and need assistance.

Using SAS to extract data from the 2010 Census (P.L. 94-171) Redistricting Data Summary Files

Using file transfer protocols (FTP) for accessing and importing the 2010 Census (P.L. 94-171) Redistricting Data Summary File data using the SAS scripts. These SAS scripts are available two ways, all three SAS import scripts combined or each one individually (GEO Header, Data File Part 1, Data File Part 2).

Additional documentation for both SAS and Microsoft Access

Additional documentation for both SAS and Microsoft Access

A listing of the components of a GEOID for commonly used geographies are provided here. These should be used when preparing the data in Access or SAS to generate the GEOID for linking to the TIGER/Line shapefiles GEOID10 field.

Geographic Support Products

TIGER/Line Shapefiles

The 2010 TIGER/Line shapefiles for all 50 states, the District of Columbia, and Puerto Rico are available for download from the U.S. Census Bureau's TIGER/Line products web page. The technical documentation for the 2010 Census Redistricting (P.L. 94-171) TIGER/Line Shapefiles can be accessed here.

TIGERweb

TIGERweb: A tool from the Census Bureau's Geography Division that allows users to visualize the 2010 census geography. This tool includes legal, statistical, and administrative areas with their geographic identifiers, as well as the transportation network, and hydrography layers in the TIGER database. In addition, it contains the 2010 Census population and housing unit counts for the various geographic entities.

Block Assignment Files

The 2010 Census Block Assignment Files and Name Look-up tables are intended for data users who want to know which blocks make up a specific geography and/or those who wish to use the demographic data without using the TIGER/Line shapefiles. The Block Assignment Files were generated for the following geographies:

  • Congressional Districts
  • State Legislative Districts
  • Voting Districts
  • School Districts
    • Elementary
    • Secondary
    • Unified
  • Incorporated Places + Census Designated Places
  • American Indian/Alaska Native/Hawaiian Homeland Areas

There is one Name Look-up table generated for each level of geography with the exception of the Incorporated Place + Census Defined Place table. For that geography there are two Name Look-up tables generated, one for Incorporated Places and another for Census Defined Places.

Relationship Files and Tallies

  • The U.S. Census Bureau's Geography Division produced 2010 Census Block Relationship Files which include crosswalk files, by state, between Census 2000 tabulation blocks and 2010 Census tabulation blocks.
  • The U.S. Census Bureau's Geography Division produced 2010 Census Tract Relationship Files which include crosswalk files, by state, between Census 2000 Census Tracts and 2010 Census Tracts.
  • A table showing the number of Census 2000 blocks, 2010 Census blocks, and the change in number between the two decennials.

Additional 2010 Census Resources

Military Vessel Errata

The Census Bureau was alerted to an error with some census block level population counts involving the locations of military vessels. This was discovered after the release of the 2010 Census (P.L. 94-171) Redistricting Data Summary Files. It was determined that this error was the result of a geocoding discrepancy. Such discrepancies can occur when a living quarter, such as a house, apartment, or military vessel, is placed in an incorrect location. The Census Bureau identified this as a limited systematic error and provided corrections in the form of errata that states could choose to use when developing their redistricting plans.

Count Question Resolution Program

The Census Bureau established the 2010 Census Count Question Resolution (CQR) Program by which State, local and Tribal area elected officials could challenge their jurisdiction's 2010 Census counts. On June 1, 2011, the Count Question Resolution (CQR) Program began accepting 2010 Census challenge submissions. All challenges were required to be received by the Census Bureau no later than June 1, 2013.

Advance Group Quarters File

The Census Bureau, in response to Federal officials, state officials, and other data users, provided an early version of Table P-42 from the 2010 Census Summary File 1, showing the seven types of group quarters. No characteristics of the group quarters were provided. The institutionalized group quarters categories include correctional facilities for adults, juvenile facilities, nursing facilities/skilled-nursing facilities and other institutional facilities; while the non-institutionalized group quarters categories include college/university student housing, military quarters and other non-institutional facilities. Data are provided for states, counties, census tracts and blocks. This table is only available via FTP.

This early release of data on the group quarters population was beneficial to many data users including those in the redistricting community who must consider whether to include or exclude certain populations in redrawing boundaries as a result of state legislation. It permitted state and local redistricting officials to overlay this file with the 2010 Census (P.L. 94-171) Redistricting Data Summary File data. Three states (Delaware, Maryland and New York) have legislation requiring the use of group quarters data in their line drawing. Other states, Hawaii and Kansas, exclude or reallocate military and college students populations.

In addition, this product may have been useful in determining if a geocoding error had occurred. The Count Question Resolution (CQR) Program provided state, local, and tribal governments the opportunity to challenge their 2010 Census housing unit and group quarters counts. The CQR program began June 1, 2011, prior to the release of the 2010 Census Summary File 1.

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