Monetary union and financial integration

Since the creation of the euro, capital ows among member countries have been large and volatile. Motivated by this fact, I provide a theory connecting the exchange rate regime to nancial integration. The key feature of the model is that monetary policy aects the value of collateral that creditors seize in case of default. Under exible exchange rates, national governments can expropriate foreign investors by depreciating the exchange rate. Anticipating this, investors impose tight limits on international borrowing. In a monetary union this source of exchange rate risk is absent, because national governments do not control monetary policy. Forming a monetary union thus increases nancial integration by boosting borrowing capacity toward foreign investors. This process, however, does not necessarily lead to higher welfare. The reason is that a high degree of nancial integration can generate multiple equilibria, with bad equilibria characterized by inecient capital ights. Capital controls or scal transfers can eliminate bad equilibria, but their implementation requires international cooperation