If potential output growth rates differ, actual growth rates can differ as well. They do not necessarily indicate a lack of real convergence. VI In the longer run, stability must be built on economic integration. An extensive body of theory has evolved on the characteristics of optimum currency areas. Most important is, that prices and wages must be able to adjust flexibly.
Mobility of goods, labour and capital shall provide for market integration. Therefore central criteria call for a high degree of structural convergence. We have to distinguish between different types of structural differences. Most critical are structural differences that may hamper market integration. These structural differences we must work to abolish as they may hamper the functioning of the monetary union.