Policy horizons in West European parliamentary systems

Abstract This paper investigates the hypothesis that coalition behaviour in West European parliamentary systems is conditioned by the existence of 'policy horizons' that delimit the extent to which parties can compromise on policy positions in order to participate in government. The first part of the paper demonstrates that policy horizons are implied by certain conceptions of party utility and that their existence would entail important constraints on the coalition game; in particular, they would produce equilibrium outcomes in some situations where voting cycles would normally be expected and they would tend to confine possible outcomes to central locations in the policy space in the absence of equilibria. The paper then develops a method of estimating policy horizons empirically in order to show that they account to a substantial extent for both the size and party composition of governing coalitions in these systems.