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Connecting the Congress: A Study of Cosponsorship Networks

Published online by Cambridge University Press:  04 January 2017

James H. Fowler
Department of Political Science, University of California, Davis, One Shields Avenue, Davis, CA 95616
E-mail address:


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 that is commonly used as a proxy for legislative influence. It also predicts roll call vote choice even after controlling for ideology and partisanship.

Research Article
Copyright © The Author 2006. Published by Oxford University Press on behalf of the Society for Political Methodology 

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Author's note: I would like to thank Tracy Burkett, Diane Felmlee, Jeff Gill, Ben Highton, Bob Huckfeldt, Jonathan Kaplan, Mark Lubell, Mark Newman, Mason Porter, Brian Sala, and Walt Stone for helpful comments and Skyler Cranmer for research assistance. This paper was originally prepared for presentation at the 2005 Midwest Political Science Association and American Political Science Association annual conferences. A copy of the most recent version can be found at


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