Political Fragmentation and Government Stability: Evidence from Local Governments in Spain
利用断点回归设计，发现西班牙地方议会中每增加一个政党，现任政府被推翻的概率提高5个百分点，原因在于单一政党多数概率降低及无多数时政府更不稳定。
This paper studies how political fragmentation affects government stability. Using a regression discontinuity design, we show that each additional party with representation in the local parliament increases the probability that the incumbent government is unseated by 5 percentage points. The entry of an additional party affects stability by reducing the probability of a single-party majority and increasing the instability of governments when such a majority is not available. We interpret our results in light of a bargaining model of coalition formation featuring government instability.