Does increasing district magnitude increase the number of parties? Evidence from Spain, 1982-2011

- District-level results from Spain, which redistributes seats while holding districtboundaries constant, provide evidence that exogenous changes in district magnitude change electoral dynamics.
- Adding seats to a district does not change the number of parties that run.
- Adding seats to a district results in increased fragmentation of votes and more parties winning seats in the election after district magnitude has increased.
- These results provide evidence that changes in electoral rules can reshape shape electoral patterns, although their effect is largest in small districts where fewer opportunities for small parties exist.