An awareness of the need to assign powers to a European institution – powers which previously were exercised primarily at national level – can only arise after the failure of the decentralised approach. This kind of choice cannot however be taken for granted because no institution, national or international, readily surrenders its powers to another body.
For example, it is not possible to determine in theory if the euro area is an optimum currency area according to pre-established objective criteria. A thorough analysis would probably stipulate the opposite.