Community Structure in Congressional Cosponsorship Networks
Physica A, Vol. 387, No. 7, pp. 1705-1712, March 2008
5 Pages Posted: 20 Aug 2007 Last revised: 19 Aug 2008
Date Written: August 8, 2007
We study the United States Congress in terms of the network between Members of Congress and the legislation that they cosponsor. Using the concept of modularity, we identify the community structure of legislators, as connected via sponsorship/cosponsorship of the same legislation, to investigate the collaborative communities of legislators in both chambers of Congress. This analysis yields an explicit and conceptually clear measure of political polarization, demonstrating a sharp increase in partisan polarization which preceded and then culminated in the 104th Congress (1995-1996), when Republicans took control of both chambers. Although polarization has since waned in the U.S. Senate, it remains at historically high levels in the House of Representatives.
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