For decades, critics of pluralism have argued that the American interest group system exhibits a significantly biased distribution of policy preferences. We evaluate this argument by measuring groups’ revealed preferences directly, developing a set of ideal point estimates, IGscores, for over 2,600 interest groups and 950 members of Congress on a common scale. We generate the scores by jointly scaling a large dataset of interest groups’ positions on congressional bills with roll-call votes on those same bills. Analyses of the scores uncover significant heterogeneity in the interest group system, with little conservative skew and notable inter-party differences in preference correspondence between legislators and ideologically similar groups. Conservative bias and homogeneity reappear, however, when weighting IGscores by groups’ PAC contributions and lobbying expenditures. These findings suggest that bias among interest groups depends on the extent to which activities like PAC contributions and lobbying influence policymakers’ perceptions about the preferences of organized interests.
Assessing the Composition and Diversity of the Australian Interest Group System
