Collapsing into the Singularity: Interest Group Polarization in American Politics


Dominic Cognata, Corey Kniss


  • Sean Kelly, Professor of Political Science, California State University Channel Islands
  • Geoffrey Buhl, Associate Professor of Mathematics, California State University Channel Islands

In recent years the House of Representatives and the Senate have been gridlocked. The recent government shutdown is a case study in the ideological polarization of political parties, and the policy gridlock that results. In short, the “political center” has collapsed leaving little “space” for compromise between liberals and conservatives. One potential explanation for this is the proliferation of liberal and conservative interest groups in Washington, DC. Many interest groups “score” legislators according to whether they voted in favor or against the group on specific roll call votes. By announcing their vote preferences, Interest groups hope to influence the votes of Congress. In turn, legislators seek to maximize their score by voting with favorite groups to improve their liberal or conservative “credentials.” Using Poole and Rosenthal’s NOMINATE algorithm—which is routinely used to estimate the ideal points of legislators—we estimate policy ideal points for a range of interest groups on budget, tax, and appropriations votes. We do this by treating interest groups as voters in Congress and implementing the NOMINATE algorithm. In the context of this algorithm we are able to locate these interest groups in a two dimensional policy space over time (1947-2011). Our findings suggest that interest groups have increasingly collapsed into a single dimension of the two dimensional space, the ideological dimension. This is consistent with Poole and Rosenthal’s finding that Congress is also collapsing into a single dimension. We conclude by speculating why this has happened.

Presented by:

Dominic Cognata, Corey Kniss


Saturday, November 23, 2013




Poster Session 2 - Villalobos Hall

Presentation Type:

Poster Presentation


Political Science