Mainstream or Ideological Outlier? The Nature of the European Union Interest Group System

Interest groups are frequently criticized for their lack of representativeness. Schattschneider explained how they `characteristically organize minorities' (1948, p. 17) and that the interest group system as a whole is biased and `sings with a strong upper class accent' (Schattschneider, 1960, pp. 34–35). At the same time, most studies of bias focus on the relative representation of different types of interest groups rather than how extreme the policy views of these groups are. In this article, we explore the ideological composition of the EU interest group system by developing and applying a method to scale the ideology of the EU population of interest groups and Members of the European Parliament based on social media activity. Our analysis allows us to explore variation in ideology among EU interest groups and the alignment of these groups relative to the political parties. The results have important implications for our theoretical understanding of the nature of the EU interest group system.