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Blog Post · January 19, 2022

Understanding the Geography of California’s Final Redistricting Maps

photo - Aerial View of Residential Neighborhood in Los Angeles

California’s Citizens Redistricting Commission (CRC) recently approved final political districts for the state. Barring legal action, these new districts will define the playing field for the next 10 years of state legislative and congressional races.

We recently looked at the racial/ethnic representation and expected partisan outcomes of the new maps. But the CRC is also required to pay attention to a variety of geographic goals, including the shape of the districts and how they relate to other political jurisdictions. We examine these constraints here. Overall, the new districts are about as respectful of geography as the current districts. But they are notably better at keeping cities intact—and marginally worse on features like compactness.

California established the CRC through a pair of initiatives passed in 2008 and 2010. The districts in place at the time had been drawn in 2001 by the state legislature in a bipartisan agreement that protected sitting incumbents of both parties at the expense of most other goals. This “bipartisan gerrymander” provoked a backlash, with many pointing to its strangely shaped districts as a sign that something was wrong.

The CRC law that emerged in reaction to this plan set several geographic goals for the new commission. In order of priority, the CRC was supposed to:  1) avoid splitting cities, counties, and communities with common interests (“communities of interest”) into multiple districts; 2) maximize compactness by combining neighboring communities instead of distant ones where possible; and 3) “nest” two assembly districts within each senate district for continuity of representation across state legislative chambers.

Yet the law also ranked these geographic goals lower than the twin goals of equal district population and compliance with the Federal Voting Rights Act. Any conflict had to be resolved in favor of these two mostly non-geographic objectives.

The first CRC was able to draw better maps on all these dimensions in part because the legislature’s 2001 plan had focused so heavily on incumbent protection to the exclusion of all else. Ironically, it was always going to be harder for the second CRC to improve on the first CRC’s product, because both commissions were pursuing the same goals. That made trade-offs between one dimension and another more likely.

The table below compares the final maps to both the current maps and the draft maps released in November on most of these geographic dimensions. (Communities of interest have no consensus definition so we do not analyze them here.) The final maps keep about as many counties intact as the current maps, and more counties than the draft maps. Like the draft maps, they keep significantly more cities intact overall.

The sacrifices came instead in the lower-priority items of compactness and nesting. The new maps are all less compact than the current ones, according to a popular measure of compactness called the Polsby-Popper score. They are even somewhat less compact than the November drafts. Similarly, nesting has taken a turn for the worse: the average number of assembly seats nested in senate seats (5.40) has reached a new high (with perfect nesting, this value would be exactly 2.0). But these differences are small compared to the 2001 map that motivated the creation of the CRC in the first place. For example, the new congressional map is 0.03 less compact on Polsby-Popper than the current map; the 2001 congressional map was 0.11 less compact on the same scale (higher values mean greater compactness).

Overall, then, the CRC has made few improvements on the geographic dimensions of the new redistricting plans, and in some ways the outcomes are marginally worse. But the CRC may have chosen to downplay geographic goals to achieve higher ranked ones: the commission made significant efforts to expand Latino representation, a higher-ranked goal, and made the most sacrifices in compactness and nesting, the lowest-ranked goals. This is a natural outcome of the prioritization they were given, especially in the context of an existing map that was already designed to meet the same criteria. Thus, while the CRC’s product is not a uniform improvement over the status quo, it appears that the commission pursued the priorities laid out for it in law.


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