Abstract
Recent work suggests that the most fruitful approach to accounting for variations in interest
system diversity of any type lies in understanding variations in interest system density (Lowery, Gray and
Fellowes 2005). We build on this insight by examining the sources of variation in the substantive
diversity of health interests in the American states, focusing on how the densities of several sub-guilds of
health interest organizations vary in their responses to changes in the sizes of the constituencies that give
rise to them and variations in the policy and political energy supporting their mobilization. We discuss
the concept of interest system diversity in the first section of the paper, highlighting its multiple meanings
and the limits of prior research. This is followed by a close empirical examination of 14 sub-guilds of
state health interest organizations. We conclude by discussing the inherent difficulties of understanding
interest system diversity.
Convention