There is a plethora of studies on interest groups in the European Union. While these studies
have generated a wealth of insights, it is not actually clear what they have accomplished. This
Living Review seeks to identify those areas of interest group studies in which our knowledge
is fairly consolidated and in which major research gaps or major controversies can be noted.
I argue that these research gaps and controversies stem from both the empirical variance in
the interest group landscape and the theoretical segmentation of EU interest group studies.
These have been shaped by influences from Comparative Politics, International Relations, Policy
Analysis, and Democratic Theory. I suggest that future research should engage to a greater
extent in cross-cutting theoretical debates in order to overcome the pronounced demarcation
of research areas and in more rigorous theory testing than has sometimes been the case. The
article starts by discussing the problem of conceptualizing interest groups before moving on
to the fissured theoretical landscape. Thereafter, major research themes are discussed. First, I
review the relation between EU institutions and interest groups. Here, I look both into multilevel
governance and Europeanization studies that focus on the vertical interaction and into analyses
that stress the horizontal segmentation of the EU system in different institutions and sectors.
Second, I analyze core themes of EU and comparative interest group studies, namely the issue
of collective action, the access of interest groups to policy-makers and their influence on EU
policymaking.
Prof. Dr Wolfgang Schumann on 25 May 10From the outset, European integration was about the transfer of powers from the national to the European level, which evolved as explicit bargaining among governments or as an incremental drift. This process was reframed with the competence issue entering the agenda of constitutional policy. It now concerns the shape of the European multilevel polity as a whole, in particular the way in which powers are allocated, delimited and linked between the different levels. This Living Review article summarises research on the relations between the EU and the national and sub-national levels of the member states, in particular on the evolution and division of competences in a multilevel political system. It provides an overview on normative reasonings on an appropriate allocation of competences, empirical theories explaining effective structures of powers and empirical research. The article is structured as follows: First, normative theories of a European federation are discussed. Section 2 deals with legal and political concepts of federalism and presents approaches of the economic theory of federalism in the context of the European polity. These normative considerations conclude with a discussion of the subsidiarity principle and the constitutional allocation of competences in the European Treaties. Section 3 covers the empirical issue of how to explain the actual allocation of competences (scope and type) between levels. Integration theories are presented here in so far as they explain the transfer of competence from the national to the European level or the limits of this centralistic dynamics. Normative and empirical theories indeed provide some general guidelines for evaluation and explanations of the evolution of competences in the EU, but they both contradict the assumption of a separation of power. The article therefore concludes that politics and policy-making in the EU have to be regarded as multilevel governance (Section 4). The main theoretical approaches and r