California Votes!
- Special Election Nov 4th, 2025
- Only statewide item: Proposition 50
Current Map
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Proposed Map
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Measures of Partisan Redistricting
Mean-Median Score Suppose we observe an election where the vote share for Republicans in each of \(n\) districts is \(v_1, \ldots, v_N\).
The mean-median score is:
\[
M = \textrm{mean}(v_i) - \textrm{median}(v_i)
\]
Measures of Partisan Redistricting
Suppose two parties, A and B. The efficiency gap (EG) favoring party A for a given pattern of votes, is defined as the difference in wasted votes divided by the total number of votes:
\[
EG = \frac{W_B - W_A}{T}
\]
Where \(W_B\) is the number of wasted votes by Party B, \(W_A\) is the number of wasted votes by Party A, and \(T\) is the total votes cast.
Research Question
Will adoption of a new district map lead to an increase in partisan advantage relative to 2024?
If so, by how much?
Words of Wisdom
Moon Duchin, from Political Geometry:
Things I Don’t Believe In
- Presenting any single number as a metric of fairness
- Especially any single number with a prescribed ideal
- Redistricting as optimization
Things I Do Believe In
- Using quantitative information to tell a qualitative story
