From the introduction of the editors:

The future borders of the European Union are explored by Jan Priewe. He argues that there is today much debate on the further enlargement of the EU. These extensions make the EU – and probably also the EMU – more heterogeneous in terms of the real economy. As the architecture of the EU was designed as a one-club-union, the paper raises the question as to how heterogeneous both the EU and EMU can and should be. To this end, the theories of optimum currency areas are reviewed which evolved from rather strong real convergence as entry criterion to concepts that allow for more heterogeneity. But the latter versions are not fully convincing. The paper puts forward five propositions: (i) the EMU should be made more homogenous, requiring much more deepening towards a political union; (ii) the countries with a lower income level are better served with keeping their currency with a special exchange rate regime compared to EMU membership; (iii) there is the case for a EU membership without access to EMU which requires specific new rules; (iv) for some countries a special status as ‘associated’ EU members within the framework of a European neighbourhood policy could be a better alternative; (v) the entry criteria for EU membership should be refined and the Maastricht- convergence criteria ought to be changed in order to include realeconomy criteria.