There is a broad consensus among economists that the increased interdependence that comes from sharing a common currency and a single monetary policy justifies some degree of economic policy coordination between euro area Member States. However, empirical studies have, thus far, offered inconclusive evidence regarding the comparative importance of different types of economic spillover. Accordingly, estimates of the welfare gains from economic policy coordination in the euro area have varied considerably. This study presents original research on the nature of economic interdependence under European Economic and Monetary Union. Its main contribution is to provide plausible estimates of the sign and size of economic spillover in the euro area and the welfare gains from economic policy coordination. These results are relevant for the European Commission's ongoing work on strengthening economic governance in the context of the Stability and Growth Pact and the Lisbon Strategy.