Should a subset of member states of a federation be allowed to form a sub-union on some policy issue? When centralization is not politically feasible, allowing an enhanced cooperation agreement among a subset of countries permits the latter to gain benefits which would otherwise be lost....

Labor mobility is commonly taken as a property of an optimal currency area. But how does that property affect the outcome of fiscal policies? In our model, we show that perfect (costless) labour mobility is not necessarily welfare improving, since it prevents the national fiscal authorities from...