The EU’s traditional approach to enlargement has relied on the Copenhagen Criteria and acquis compliance as the measures to judge a candidate’s suitability for membership. However, these measures do not say much about the candidate’s actual readiness to assume both the burdens and privileges of membership. Instead, it is essentially assumed that competitiveness and convergence will more or less automatically follow from deeper integration.

This paper challenges that assumption. By following a different methodology, based on the concept of ‘Integration Maturity’, it suggests that a series of economic indicators, as well as the candidate’s economic performance over time, will better reflect a candidate’s preparedness to benefit from deeper integration, or, alternatively, suggest that more time should be spent achieving sufficient competitiveness and convergence.

To illustrate this point, this paper examines the cases of Slovenia and Croatia, who joined the EU in 2004 and 2013, respectively. Both had been part of Yugoslavia, and therefore had similar starting points for their economic transitions in the 1990s. Yet, while the former has prospered since accession, the latter is one of the worst performing members. What this paper suggests is, that this divergence was entirely predictable, based on the two countries’ economic performance on several indicators during the years leading to accession. This finding has implications for the way future accessions should be assessed, especially as the EU has recently decided to open accession talks with several more countries, and since politics may well trump economic considerations.