Cosponsorship Data
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Transcript of Cosponsorship Data
Cosponsorship Data 280,000 “bills” proposed in the U.S. House and
Senate from 1973 to 2004 (93rd-108th Congresses) recorded in Thomas
over 2.1 million cosponsorship signatures partitioned by chamber and Congress to create
32 separate cosponsorship networks http://jhfowler.ucsd.edu/cosponsorship.htm
Cosponsorship in the House
Cosponsorship in the Senate
Mutual Cosponsorship Relations
Connectedness: An Alternative Measure Traditional measures of centrality generate plausible names None takes advantage of information about the strength of social
relationships Total number of cosponsors on each bill
Legislators recruit first those legislators to whom they are most closely connected. More cosponsors = lower probability of direct connection Bills with fewer total cosponsors more reliable Strength of the connection between i and j = 1/cij
Total number of bills sponsored by j and cosponsored by i More bills in common = stronger relationship
Weighted cosponsorship distance
Weighted cosponsorship distance
Legislative connectedness Suppose direct distance from legislator j to legislator i is simple
inverse of the cosponsorship weight Then use Dijkstra’s algorithm (Cormen et al. 2001)
Starting with legislator j, identify from a list of all other legislators the closest legislator i
Replace each of the distances with Remove legislator i from the list and repeat until there are no more
legislators on the list. Connectedness is the inverse of the average of these distances from all other legislators to legislator j.
Results for the House
Results for the Senate
Quality of Strongest Weighted Relationships Institutional Ties
House committee chairs and ranking members Senate majority and minority leaders
Regional Ties From the same state In the House they are often from contiguous districts
Issue Ties Rep. Jim DeMint and Sue Myrick -- Republican Study Committee Sen. George Mitchell and Jim Sasser -- Federal Housing Reform Sen. Kay Bailey Hutchinson and Sam Brownback -- marriage penalty relief and
bankruptcy reform Personal Ties
Senator John McCain chaired Senator Phil Gramm’s 1996 Presidential campaign McCain has told the media that they have been friends since 1982 when they
served together in the House (McGrory 1995)
108th House Top 20
108th Senate Top 20
External Validity: Legislative Influence
Widely used measure of legislative influence is number of successful floor amendments Hall 1992; Sinclair 1989; Smith 1989; Weingast
1991 1 SD increase in connectedness increases
successful floor amendments 53% in House 65% in Senate
External Validity: Roll Call Votes
Model roll call votes as in Poole and Rosenthal, adding connectedness score of sponsor
1 SD increase in connectedness of sponsor increases votes for bill by 5.2 in House 8.2 in Senate
2 SD increase would change 16% of House votes and 20% of Senate votes
Landmark Legislation:An Alternative to Mayhew
Modularity(Newman and Girvan 2004)Define modularity to be
Q = (number of edges within groups) – (expected number within groups).
Actual Number of Edges between i and j is
Expected Number of Edges between i and j is
Modularity Matrix So Q is a sum of
over pairs (i, j) that are in the same group Or we can write in matrix form as
Where B is a new characteristic matrix, the modularity marix,
(si, sj)
Modularity Matrix
Algorithm Calculate the leading eigenvector of the
modularity matrix Divide the vertices according to the signs of the
elements
Note that there is no need to forbid the solution with all the vertices in a single group.
Example
Example Applications Books on politics
The vertices represent 105 recent books sold from Amazon.com
Divide the books according to their political alignment Liberal / Conservative / Centrist
Example
Polarization in the 108th Senate
108th House by Party
108th House by Ideology
108th House by State
108th House by Committee
Polarization Over Time in the House
Polarization Over Time in the Senate
Black Legislators in the 103rd House
Black Legislators in the 104th House
Black Legislators in the 108th House
Poor Districts in the 108th House