CID | CA Congressional Districts Mapping Tool

This mapping tool presents population and voter data for the newly redrawn California Congressional Districts. These congressional districts replace the districts generated by the current California Citizens Redistricting Commission due to the passage of Proposition 50. Click the map to use the tool.

About The Tool

The tool is made available to help inform the public about California's newly redrawn congressional districts. CID is a nonpartisan academic research center.

This project is supported by a grant from the Evelyn and Walter Haas, Jr. Fund.

Methodology

Data Sources used for the tool are the following: California Voter Files, Assembly Bill 604 Files, and the Redistricting Data Hub. Current methods in election science used to identify the race and ethnicity of voters in official voter files are less reliable for some demographic groups, including Indigenous/Native and Asian American subgroup populations. We identified registrants’ race and ethnicity in county voter files with the R package Who Are You (WRU), which computes the probability of each racial category for registrants using surname, neighborhood demographics (geocoding with census tract data), and other characteristics, such as gender, party and age. For this tool, analysis of the voter file by race and ethnicity is limited to Latino, Asian American, Black, and white, non-Latino registrants because imputation for other racial and ethnic groups can have a high degree of inaccuracy. However, some errors in measurement are present for these groups, particularly for Black and white, non-Latino registrants, and caution is appropriate when interpreting effects.