The Interest Group Portfolio

What makes an interest group influential? In a new article in Interest Groups and Advocacy (currently ungated), Michael Heaney and Geoffrey Lorenz argue that a group becomes influential not because of its work in a single coalition, but rather because of its larger portfolio of work in various coalitions on a range of policy issues. However, groups can't always develop such a portfolio by their own choices; the broader alliance-forming patterns of other interest groups will influence the path they take. From the abstract:

We evaluate these hypotheses using a study of 115 interest groups involved in the enactment and implementation of the Medicare Modernization Act of 2003. This legislation established an outpatient prescription drug benefit in Medicare – a government health insurance program for the elderly and disabled in the United States – and made other significant changes to the program. We conducted personal interviews with representatives of 102 of these groups. We analyzed data resulting from these interviews using negative binomial and ordinary least squares regression models. The results [suggest that]... groups gain influence over the policy process when their coalition portfolios increase the extent to which they are situated between other groups in the coalition network. However, interest groups are limited in the extent to which they can create portfolios that have desirable levels of betweenness because network position is also a function of membership decisions made by all other groups in the network. These results provide insight into how the composition of coalition portfolios affects the ability of interest groups to exert influence over the policy process. This analysis is most directly applicable to policy debates over complex pieces of legislation.