Connecting the Congress: A Study of Cosponsorship Networks

47 Pages Posted: 20 Aug 2007

See all articles by James H. Fowler

James H. Fowler

UC San Diego Division of Social Sciences; UC San Diego School of Medicine


Using large-scale network analysis I map the cosponsorship networks of all 280,000 pieces of legislation proposed in the U.S. House and Senate from 1973 to 2004. In these networks a directional link can be drawn from each cosponsor of a piece of legislation to its sponsor. I use a number of statistics to describe these networks such as the quantity of legislation sponsored and cosponsored by each legislator, the number of legislators cosponsoring each piece of legislation, the total number of legislators who have cosponsored bills written by a given legislator, and network measures of closeness, betweenness, and eigenvector centrality. I then introduce a new measure I call 'connectedness' which uses information about the frequency of cosponsorship and the number of cosponsors on each bill to make inferences about the social distance between legislators. Connectedness predicts which members will pass more amendments on the floor, a measure which is commonly used as a proxy for legislative influence. It also predicts roll call vote choice even after controlling for ideology and partisanship.

Suggested Citation

Fowler, James H., Connecting the Congress: A Study of Cosponsorship Networks. Political Analysis, Vol. 14, No. 4, pp. 456-487, Fall 2006. Available at SSRN:

James H. Fowler (Contact Author)

UC San Diego Division of Social Sciences ( email )

9500 Gilman Drive
Code 0521
La Jolla, CA 92093-0521
United States


UC San Diego School of Medicine ( email )

9500 Gilman Drive
MC 0507
La Jolla, CA 92093
United States


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