Voting Equilibria Under Proportional Representation

This article studies the consequences of strategic voting by outcome-oriented voters in elections under proportional representation (PR). I develop a model of elections under PR, in which voters choose among an arbitrary finite number of parties, and the policy outcome is determined in a postelection bargaining stage. I use a new solution concept, robust equilibrium, which greatly mitigates the well-known problem of indeterminate predictions in multicandidate competition. Applying the equilibrium concept to the model, I find that PR promotes representation of small parties in general, even when voters are strategic. However, the median voter plays a critical role in shaping policy outcomes, which reflects the majoritarian nature of parliamentary policy making rules. Thus, PR may not be incompatible with the majoritarian vision of representative democracy if voters' main concern is policy outcomes.