Constitutional veto players : a formal quantitative model

The veto player theory is a branch of political science that applies the toolset of social choice theory and game theory to the analysis of the effect of institutional arrangements on political decision-making processes. It does so by assuming that there exists a continuous policy space and a discrete set of institutional or political players whose preferences are determined by metrics that frame the policy space, and that is possible to translate formal and informal rules governing decision-making processes into a set of possible winning coalitions, and that a coalition will approve a policy change only if it represents a Pareto improvement over the status quo for all of its members. Unfortunately, the standard veto player models cannot correctly account for constitutional veto players, i.e., those who need to justify their disapproval of a policy change in constitutional terms. We propose an extension of such models that is capable of incorporating such players and demonstrate how their incorporation affects the efficiency of the political system, understood as a measure of the set of possible policy changes.