For a club such as the European Union, an important question is when, and under which conditions, a subset of the members should be allowed to form "inner clubs" and enhance cooperation. Flexible cooperation allows members to participate if and only if they benefit, but it generates a freerider...

Our paper proceeds as follows: As a point of departure, part two highlights the heterogeneity among EU member states following the recent enlargement, while part three reviews three main alternative conceptions of flexible integration as they were discussed in political circles. Part four...

In many organizations, decisions are taken by unanimity giving each member veto power. We analyze a model of an organization in which members with heterogenous productivity privately contribute to a common good. Under unanimity, the least efficient member imposes her preferred effort choice on...