California has 52 congressional districts. We’ve generated 5,000 sets of randomly simulated districts according to the relevant criteria. Three of these plans are shown here, along with the actual enacted map.
Partisan Features
In California, Democrats win about 65% of the vote in a typical statewide election. Proportionally, that would translate to 34.0 Democratic seats out of 52 total.
But proportionality isn’t guaranteed, even in a fair redistricting process. In our simulated plans, Democrats won anywhere from 43.0 to 46.5 seats on average, with 45.0 being the most typical. In contrast, we expect the enacted plan to yield 44.5 Democratic seats on average, which is less than 73% of all simulated plans.
The graph below breaks this down in detail, showing how each district of the enacted plan compares to the set of simulated districts.
Gerrymandering metrics
There are other ways of measuring the partisan skew of redistricting plan. The graph below shows two these metrics. The deviation from partisan symmetry measures the expected difference in each party’s share of seats if they each won 50% of the statewide vote. The efficiency gap is calculated as the difference in the number of wasted votes for each party. These metrics may be misleading for a strongly Democratic state like California. Learn more about these metrics here.
Traditional redistricting criteria
Factors other than partisanship are important for redistricting, too. The graph below shows the geographic compactness and the number of counties which are split into multiple districts. As far as compactness, California’s enacted plan scores a 0.21, less than 96% of all simulated plans (a higher score means more compact). It splits 27 counties, compared to an average of 22 counties for our simulated plans.
Political Geography
These two maps show the partisan lean across California in a typical statewide election, and the share of minority voters around the state.
More information
Download the data for California.
Learn more about our methodology.
Elections included in analysis:
- President 2016
- President 2020
Redistricting requirements
Our algorithmic constraints used in simulations are in part are based on some of these requirements and discretionary criteria. See full documentation and code for the complete implementation details.
In California, under Article XXI, districts must:
- be contiguous (2d3)
- have equal populations (2d1)
- be geographically compact (2d5)
- preserve city, county, neighborhood, and community of interest boundaries as much as possible (2d4)
- not favor or discriminate against incumbents, candidates, or parties (2e)
- comply with the Voting Rights Act (2d2)