Interest groups in EU policy-making

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.