Measuring Interest Group Influence in the EU

How much influence do interest groups have on policy outcomes in the European Union (EU)? This question is highly relevant for both debates on the democratic legitimacy of the EU and our understanding of policy-making processes in this entity. Nevertheless, because of the difficulties inherent in measuring interest group influence, it has been addressed by only a small number of studies. The purpose of this research note is to stimulate further research by clearly identifying the methodological problems and suggesting ways of how to overcome them. In doing so, I distinguish three broad approaches to measuring interest group influence: process-tracing, assessing `attributed influence' and gauging the degree of preference attainment. Although the review reveals that all three approaches have their shortcomings, I conclude that the difficulty of measuring influence should not be exaggerated either. Methodological triangulation, `method-shopping' and larger-scale data collection should allow us to improve on the state of the art.