Generalist Interest Organizations and Interest System Density: A Test of the Competitive Exclusion Hypothesis*


  • A previous version of this article was presented at the Annual Meeting of the American Political Science Association in Washington, DC, September 2010. We thank Irwin Morris for helpful comments.

Direct correspondence to Virginia Gray, Department of Political Science, University of North Carolina at Chapel Hill, 305 Hamilton Hall, CB #3265, Chapel Hill, NC 27599 <>.



We examine the effects of interest community density on generalist interest organizations. A core element of population ecology theory is competitive exclusion, which suggests two hypotheses. First, through niche partitioning of the issue space among similar organizations and the comparative advantages of specialist organizations, generalists in heavily populated systems struggle to secure members more than their counterparts in less densely populated ones. Second, surviving generalists narrow the scope of their lobbying activities to fewer issues on which they hold comparative advantage.


We test both hypotheses through regression analysis of data on the mobilization and lobbying focus of U.S. state Chambers of Commerce.


Both participation in state Chambers and the number of bills that Chambers track decline as the business interest community becomes more densely populated.


We conclude that even state Chambers—the old bulls of the lobbying pasture—are powerfully influenced by competition among business interest organizations.