CSAC Bulletin Article

Curious about county voter registration data?
We crunched some numbers that may interest you!

November 9, 2023

Voter registration and subsequent participation at the polls is the bedrock of American democracy. One notable bright spot is the increase in voter registration in California’s counties over the last several years. Using the California Secretary of State’s odd-numbered reports of registration, we assessed voter registration data over the last ten years.

What we found is exciting – total voter registration increased from about 75.68 percent to 82.27 percent across California’s 58 counties. At first glance, a 6.59 percent increase may seem trivial. However, consider this: the increase works out to about 3.9 million more registered voters across California’s counties! For the sake of comparison, over the last ten years, California counties have added the equivalent of the entire voter rolls of eight states combined – Rhode Island, Montana, Delaware, South Dakota, North Dakota, Vermont, Alaska, and Wyoming (source: United States Census as of November 2022). To further belabor this point, the states with the 16th and 17th highest number of registered voters – Massachusetts and Arizona, respectively – have about 3.6 million registered voters each compared with the 3.9 million registered voters added to California county voter rolls over the last 10 years.

The following chart illustrates California’s voter registration trends over odd-numbered years from 2013 to 2023. As expected, following each presidential election, there is a bit of a bump in registration.

State data is fine, but what about the county data?

We’re getting there. Using CSAC’s California County Caucuses as a yardstick, we were curious if there is any difference in registration rates between Rural, Suburban, and Urban counties. Rural counties experienced the largest increase in voter registration rates, at 7.47 percent or about 143,000 registered voters. Suburban counties followed closely behind and saw an almost mirror rate of increase, at 7.38 percent or about 610,00 registered voters. Urban counties saw the smallest jump in the rate of voter registrations, at 6.37 percent, but experienced the largest increase in the actual number of voter registrations at nearly 3.2 million. The following chart aggregates voter registration by County Caucus.

The following charts illustrate the rate of voter registration over time by Rural, Suburban, and Urban counties.

Lastly, we were curious about which counties experienced the greatest rate of increased voter registration over the last 10 years by Rural, Urban, and Suburban counties. The following table reflects the top five counties by rate of increase by Rural, Suburban, and Urban counties.

Rural Counties

Suburban Counties

Urban Counties


% Increase of Reg. Voters


% Increase of Reg. Voters


% Increase of Reg. Voters





Contra Costa








Del Norte










San Bernardino






San Mateo


What does this all mean? In practical terms, voter registration throughout California’s counties underwent substantial changes over the past decade. A little over 10 years ago, the Department of Finance estimated that California’s population totaled about 38.3 million. As of January 1, 2023, the Department of Finance estimated that California population totaled about 38.9 million. While population growth has been flat, California counties continue to experience dramatic progress in voter registration, to the tune of about 3.9 million more registered voters.

Interested in more county voter registration data? Check out CSAC’s DataPile, which provides a host of relevant county voter registration data and other interesting county data points.

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