Self Enforcing Voting in International Organizations

Some international organizations are governed by unanimity rule, some others by a majority system. Still others have moved from one system to the other over time. The existing voting models, which generally assume that decisions made by voting are perfectly enforceable, have a difficult time explaining the observed variation in governance mode, and in particular the widespread occurrence of the unanimity system. We present a model whose main departure from standard voting models is that there is no external enforcement mechanism: each country is sovereign and cannot be forced to follow the collective decision, or in other words, the voting system must be self-enforcing. The model yields unanimity as the optimal system for a wide range of parameters, and delivers rich predictions on the variation in the mode of governance, both across organizations and over time. ∗We thank James Anderson, Pierpaolo Battigalli, Matt Jackson, Francois Maniquet, James Peck, Guido Tabellini and Jean Tirole for very helpful comments. Arnaud Costinot provided excellent research assistance. We also benefited from comments by workshop participants at the California Institute of Technology, the Federal Reserve Bank of Minneapolis, Carnegie Mellon University, University of Rochester, Penn State University, Duke University, INSEAD, University of Namur, Princeton University and Stockholm University. Morelli thanks the Deutsche Bank for sponsoring him as a member of the Institute for Advanced Study (Princeton) in 2001-02, when the project was conceived.