By employing a wide variety of evidence including survey data, extensive content analysis, and interviews with policy stakeholders, Matt Grossmann systematically addresses two fundamental questions about the interest group universe: which factions in society gain extensive representation by organized interests and, among those groups, which become the most prominent and influential representative agents in the policymaking arena. To answer these questions Grossmann presents two rigorous theoretical frameworks for understanding the representative role of interest groups: behavioral pluralism and institutional pluralism