The exceptional nature of the euro does not mean that Europe’s monetary union is unsustainable in the long run, or only sustainable if Europe becomes a sovereign federation. The parameters of the questions have been well stated by Mario Draghi (2012), the head of the European Central Bank, who said that “those who claim only a full federation can be sustainable set the bar too high.” Instead, Draghi focuses on the “minimum requirements to complete economic and monetary union.” In such framework, the future of the euro depends on a key political variable: the heterogeneity costs associated with the minimum set of functions that must be pooled or delegated for a currency union to work