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An Empirically Accurate Computation Model of Multiparty Electoral Competition

Most theoretic models of multiparty electoral competition make the assumption that party leaders are motivated to maximize their voteshare or seatshare. In plurality rule systems this is a sensible assumption. However, in proportional representation systems, this assumption is questionable since the ability to make public policy is not strictly increasing in voteshares or seatshares. I present a theoretic model in which party leaders choose electoral declarations with an eye towards the expected policy outcome of the coalition bargaining game induced by the party declarations and the parties' beliefs about citizens' voting behavior. The model is applied to the case of the Netherlands. Markov chain Monte Carlo is used to estimate the parties' beliefs about mass voting behavior. Due to the complexity of the parties' objective functions, equilibria are found numerically. Unlike previous models of multiparty electoral competition, the equilibrium results are consistent with the empirical declarations of the 4 major Dutch parties. These results make more clear the underlying reasons for the relative scarcity of centrist parties in highly proportional electoral systems.