Advanced Imaging of California Precincts Shows Nuanced Landscape

[courtesy of California Progress Report]

By David Latterman
Principal
Fault Line Analytics

The California Political Precinct Index (CPPI) is an ongoing project by Fall Line Analytics to better characterize detailed political voting trends in California. The CPPI is a precinct-level index which ranks each California precinct on a 0-10 0 political scale, with 0 representing the most ‘conservative’ precincts and 100 representing the most ‘liberal’ precincts’.

Taking the methodology from the well-known and highly-accurate San Francisco Progressive Voter Index, the CPPI is created by performing a factor analysis on the results of several ballot measures for every California precinct. These measures can be interpreted on a left-right ideological scale, which when taken together, reveal inherent voting patterns of the precinct. Because the precinct change in most California counties from year to year, for the CPPI only issues from 2004 were used in this initial index.

The resulting index reveals political patterns in California that have rarely been seen at so detailed a level. We clearly understand the ‘liberal coast and conservative inland’ phenomenon, but now we can see subtle nuances throughout the state; for instance, variations between the coastal cities or the towns along Rt. 99 in the Central Valley.

When the CPPI is aggregated into larger geographies like counties, California Assembly Districts, or Congressional Districts, we can see big-picture voting trends. Looking at the average CPPI scores for Assembly districts, we see very clearly how left-leaning Districts vote Democrat, and right-leaning Districts vote Republican. There is also a transition area where districts are more up for grabs, and a party not in power could claim a seat from the sitting Assemblyperson. This technique works for any district configuration, and can also work for primaries when we get a sense of which districts lean toward the extremes for their parties and which of those lean more centrist.