The increasing involvement of interest groups in international organizations (IO) is one of the most notable developments in world politics. This paper addresses the following research question: When, why, and how do interest groups influence the policy-making of IOs? Following standard conceptualizations of influence in the literature on international cooperation, the proposed paper conceives of the influence exerted by interest groups in terms of two dimensions: shaping the efficiency of IO policy-making and shaping the distributive profile of IO policy-making. From this vantage point, the paper develops hypotheses about interest group influence in IO policy-making by drawing on existing interest group research on the EU and the US. The central claim of the paper is that interest group influence in IO policy-making varies as a function of group characteristics, issue area, policy phase, and level of formal access to IOs. Empirically, the paper tests the hypotheses by using new data on formal access as well as new data from a survey among civil society and business organizations involved in the policy-making process of 5 IOs: the African Union, the Council of Europe, the Food and Agricultural Organization, the Organization of American States and the United Nations. This data set allows for a comparative analysis of perceived group influence across issue areas, phases of the policy process, and levels of access to IO policy-making. In this respect, the paper adds new theoretical insights and empirical evidence that can inform the study of interest group influence both in EU and world politics.
