On October 17, 1989, the Loma Prieta earthquake struck the central coast of California. Three weeks later, on November 7, 1989, San Francisco held a municipal election. A dozen polling places had been destroyed or were otherwise inaccessible to the public due to the earthquake, so new polling places were selected for the affected precincts in the days leading up to the election. This case represents a credible natural experiment examining how changes in the costs of voting affect political participation, with the “as-if” random assignment of voters to the treatment group determined by earthquake damage to individual buildings rather than election administration decisions which could conceivably be related to turnout, such as precinct consolidation or the location of precinct boundaries. We use a difference-in-differences design, with the difference in turnout between the 1987 and 1989 municipal elections as the outcome variable. We find that voter turnout was 2.9 [5.1, 0.6] percentage points lower in precincts in which the polling place was relocated due to earthquake damage as compared to precincts that kept their original polling place.
Comparison of 1989 Loma Prieta earthquake damage to mapped lineaments along the range front of the Santa Cruz Mountains, California