This study looks at how the characteristics of states' interest group environments affect state participation in interstate compacts. Drawing on prominent theories of interest system characteristics, we hypothesize that interest group density and concentration will influence a state's propensity to join compacts.
Method. Using pooled cross-sectional time-series event-count models, we test our hypotheses for 48 states over a 30-year period.
Results. We find that states with denser interest group systems are more likely to join interstate compacts, but that greater concentration of organized interests in a few economic sectors impedes compact formation. Additional analyses show that the effects of state interest group systems vary across types of interest groups and compacts. In particular, the effects of interest group density appear to be driven primarily by not-for-profit groups generating increased state participation in noneconomic compacts.
Conclusion. Interstate cooperation is influenced in important ways by characteristics of interest group environments.