Central to ongoing debates over the desirability of monetary unions is a supposed trade-off, outlined by Mundell (1961): a monetary union reduces transactions costs but renders stabilization policy less effective. If shocks across countries are sufficiently correlated, then, according to this argument, delegating monetary policy to a single central bank is not very costly and a monetary union is desirable. This paper explores this argument in a setting with both monetary and fiscal policies. In an economy with monetary policy alone, we confirm the presence of the trade-off and find that indeed a monetary union will not be welfare improving if the correlation of national shocks is too low. However, fiscal interventions by national governments, combined with a central bank that has the ability to commit to monetary policy, overturn these results. In equilibrium, such a monetary union will be welfare improving for any correlation of shocks.

We study the efficiency of banking regulation under financial integration. Banks freely choose the jurisdiction where to locate their activities and have private information about their efficiency level. Regulators non-cooperatively offer any regulatory contract that satisfies information and participation constraints of banks. We show that the unique Nash equilibrium of the regulatory game is a simple pooling contract: financial integration is characterized by the inability for regulators to discriminate between banks with different efficiency levels. This result is driven by the endogenous restriction caused by regulatory arbitrage on the capacity of regulators to use several regulatory instruments.