Legislative Redistricting Data Setup

• 2020 Census
  • https://www.census.gov/programs-surveys/decennial-census/about/rdo/summary-files.html
• 2010 Census
  • Download and unzip geometry files Download the Census 2010 Tiger files in Shapefile format.  As a minimum you need the TabBlock10 (Block 2010) or BG10 (Block Groups 2010) files.
  • Download redistricting files from the Census site at http://www2.census.gov/census_2010/01-Redistricting_File--PL_94-171/ .
• 2000 Census data
  • Download and unzip geometry files. Download the Census 2000 Tiger files in Shapefile format.  As a minimum you need the TabBlock00 (Block 2000) or BG00 (Block Groups 2000) files.
  • Download the redistricting files from the Census site at http://ftp2.census.gov/census_2000/datasets/redistricting_file--pl_94-171/.
• You will need two files for the state, which come together in a single file such as  md2010.pl.zip. You must then unzip them into the same directory as the geometry files.
• From MICRODEM's data manipulation form, run the "Resample, Database, TIGER redistricting" menu choice. This will add the population data to the block file. The racial categories for the 2000 and 2010 Census open a multitude of possibilities because citizens could select as many categories as they wanted. This option will put in:
  • DISTRICT: your assigned district, as a string/character field.
  • POP: The total population in the block or tract.
  • WHITE1: The white population in the block, but only for those people who selected a single racial category.
  • BLACK1: The black population in the block, but only for those people who selected a single racial category.
  • ASIAN1: The Asian population in the block, but only for those people who selected a single racial category.
  • HISPANIC: The Hispanic category, which is different from race (one can be hispanic and white or black).
  • The mismatch between the total and the sum of the white, black, and Asian will show the numbers in other racial categories, and the number who selected multiple races.
  • Racial categories by age are not considered.  This might be important if some groups have a different age profile than others.
• You can remove blocks with 0 population, which can complicate your operations, by filtering the data base and then saving the filtered database.  Blocks with 0 population include water regions, schools, industrial parks, or shopping centers.
• You must add fields for AREA_KM2 and POP_DENS.
• If you want to do a subset of the region, such as a city within a county, you can use Edit, Mask, Mask database with shapefile.
• You can use Point in area to assign each area to its membership in existing districts, and then copy that to the DISTRICT field.  This may miss a few fields, since some maps include large water areas and others do not, which can put the centroid outside the correct region.

http://www2.census.gov/census_2010/01-Redistricting_File--PL_94-171/pl_part1_2010.sas has the best description of what the fields are in the file redistricting data files.  If you want to do additional investigation of this data, perhaps to look at the distribution of self-identified multi-racial individuals, the data files are ASCII CSV but do not have a header line with the field names, and can be very large, but you could turn them into a database and then  join them to the block geometry files.

Last revision 8/13/2021