The EU’s Capacity for Enlargement: Does It Matter?

I examine the so far only vaguely defined concept of the capacity to absorb new members, known as the fourth Copenhagen criterion of the European Union (EU), in terms of its reasonability. Methodologically, the political-economic elements of this capacity to enlarge are analyzed with a model for a confederation of states that represents the trade-off between the economic benefits of size and the costs of heterogeneity of the population’s preferences in case of enlargement. The analysis shows that the political concept of "enlargement capacity" contains rational elements and is therefore relevant. The model is used to assess not only the politics and empirics of previous EU enlargements, but also the upcoming enlargement rounds with Ukraine, Moldova and the Western Balkan states. The presently intensive discussion about reforms to the EU architecture and policies, also triggered by the challenges posed by these future enlargements, can likewise be considered in terms of the trade-off between benefits of size and the costs of heterogeneity.