The Structure of Interest Group.

In this paper, we measure the structure of the Washington interest group system to explain mobilization patterns across issue areas. Interest group scholars have traditionally studied mobilization by estimating the aggregate size of the interest group system and comparing the distribution of different types of organizations. They have, not surprisingly, found that the number of occupational interests far exceeds the number of non-occupational organizations, indicating a representational bias in favor of business interests (see, e.g., Schlozman and Tierney 1986, Walker 1991, Baumgartner and Leech 2001). Yet there is reason to believe that the issues on which non-occupational organizations lobby government officials are very different from the issues that mobilize business interests, suggesting that the degree of representational bias may vary across issue areas. This paper develops a theory to differentiate descriptive issue areas in order to explain the variable nature of group involvement. To demonstrate these points we make use of data from reports filed with the U.S. House and Senate under the Lobbying Disclosure Act of 1995. Our dataset includes more than 19,000 reports filed by 6,900 organizations in 1996. The reports are filed by interest organizations and hired lobbying firms on behalf of organizational clients. Each organization that registers to lobby indicates their interests by selecting from a governmentally defined list of 74 issue areas. Therefore each organization in the dataset has a registration profile indicating the areas in which they were active, and these profiles can be compared across groups to make inferences about the structure of policy subsystems. Our analysis will use profile dissimilarity measures—a multidimensional scaling (MDS) technique—to construct a geometric model of the 74 issue areas and the individual groups (Davison 1992). We expect the MDS analysis to yield a spatial configuration of the interest group system in two orthogonal dimensions: an economic-social policy dimension and distributive-benefits dimension (Jacoby and Schneider 2001). Because the resulting scale values will be interval-level measures of their locations on each of the dimensions, they can be correlated with measures of group activity levels in each issue area. We hypothesize that the business advantage will be more pronounced for economic policies than for social issues. Likewise, we expect the business interest bias to be greater for policies with particularized benefits than those with common goods. Thus, assessing the structure of the Washington group system gives us insight into the variable nature of mobilization bias in a way that measures of aggregate size and scope cannot. [ABSTRACT FROM AUTHOR]