Coalition Inclusion Probabilities. A Dynamic Measure of Party Competitiveness

• In Event: Bargaining and Policy-making in Multiparty Governments

Abstract

Because parties in government influence policy the most, coalition inclusion prospects would seem predictive of the behavior of office- and policy-seeking parties. But coalition models are designed for explanation more than prediction. Most empirical models predict coalition composition rather than individual parties’ coalition probabilities; neither calculate bargaining leverage between elections and neither test their predictions out of sample. We combine coalition formation models optimized for prediction with a large set of political polls to estimate coalition inclusion probabilities for parties in a sample of 21 parliamentary democracies at a monthly frequency over four decades. The probability of entering or remaining in an alternative government -- i.e., bargaining leverage -- serves as a strong predictor of party behavior, markedly superior to polls and expected seat shares. We demonstrate our measure's utility with applications to no-confidence motions and the stringency of environmental policies.

Authors

• Mark A. Kayser, Hertie School of Governance, Berlin

• Jochen Rehmert, Hertie School of Governance