The California Voting Rights Act: Utilizing Bayesian Improved Surname Geocoding (BISG) on the 2025 Special Election Voter File

The UCLA VRP, in partnership with the California Secretary of State's office, has published a new report providing a comprehensive overview of voting in California Voter's Choice Act (VCA) counties during the November 2025 Special Election. The purpose of this analysis is to report patterns by voter characteristics for all California voters, and to identify opportunities for improved voter mobilization in future elections.

Read the full report here.

VRP Data Team Documents USPS Late Delivery of Ballots

New analysis from the UCLA Data Science Team documents an increase in vote-by-mail ballots rejected after arriving beyond California’s allowable seven-day grace period. In the November 2025 election, 72,169 ballots were submitted by voters but did not arrive at county election offices until after the seven-day deadline. These ballots accounted for 44.5% of the 162,160 vote-by-mail ballots rejected overall. This finding comes from the VRP's report written in partnership with the CA Secretary of State's office, The California Voting Rights Act: Utilizing Bayesian Improved Surname Geocoding (BISG) on the 2025 Special Election Voter File. Read the full report here.

Given the politicization of USPS delivery of vote-by-mail ballots, the UCLA VRP will continue studying how and why these ballots arrive at county offices too late to be processed, ensuring all voters have an equal opportunity for their vote to be counted.

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