Interest Group Influence on Decision-making Outcomes in Bicameral Political Systems

The project investigated the determinants of interest group influence in political systems. In order to influence policy outcomes, interest groups may choose to lobby several political actors. But not all political actors are created equal. Depending on preference configurations and formal powers of the decision-makers, the interest groups problem is to identify the most promising lobbying targets. The major focus of the project was therefore to analyze how the institutional setup in bicameral systems influences interest groups' choice of communication strategy. The first step taken to answer this question was the development of a formal theoretical model to explain interest groups' interaction with several decision-makers. In a second step, the model was tested empirically using data on lobbying strategies for the USA and Germany. The data comprise important legislative acts in the policy fields of labor and social policy. We find that despite differences in the organization of interests between the two systems there is a common underlying pattern of communication strategies if one focuses on interest group communication with structurally equivalent decision-makers in the two political systems. The issue context and other factors which are usually highlighted as determinants of interest group actions are less important determinants of communication patterns than commonly thought.