Overlapping regionalism in Europe: Patterns and effects

European states have not only joined several regional organizations (ROs) over time, but ROs’ policy competencies have also broadened in scope. As a result, states are exposed to overlapping regionalism, defined as the extent to which ROs share member states and policy competencies at the same time. First, this article identifies patterns of overlapping regionalism in Europe. In second step, it sheds light on consequences from overlapping regionalism for RO effectiveness, more particularly non-compliance. We argue that an increase in the extent to which a member state is exposed to overlapping regionalism increases its probability for violations of RO norms and rules, which reduces RO effectiveness. When states have joined more ROs with similar policy competencies, the number of rules and norms that need to be complied with is higher. Non-compliance also becomes more likely when these rules and norms are not identical or even incompatible.