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
Congress
House
93rd
94th
95th
96th
97th
98th
99th
100th
101st
102nd
103rd
104th
105th
106th
107th
108th
Years
1973-1974
1975-1976
1977-1978
1979-1980
1981-1982
1983-1984
1985-1986
1987-1988
1989-1990
1991-1992
1993-1994
1995-1996
1997-1998
1999-2000
2001-2002
2003-2004
Mean
Mean
“Bills”
“Bills”
Sponsored Cosponsored Mean Cosponsors
by Each Cosponsors
per
Total Total by Each
Mean
Sponsors“Bills” Legislator Legislator per “Bill” Legislator Distance
442
439
437
436
435
435
432
436
438
436
437
433
439
437
441
438
20994
19275
18578
10478
10062
9095
8606
8093
8423
8551
7464
6558
6780
7894
7541
7636
48
44
42
24
23
21
20
18
19
19
17
15
15
18
17
17
129
151
170
187
223
297
329
341
370
339
259
168
219
278
273
276
3
3
4
8
10
14
17
18
19
17
15
11
14
15
16
16
70
79
93
111
132
157
171
174
184
172
144
105
127
151
143
147
1.95
1.89
1.83
1.76
1.72
1.65
1.61
1.60
1.58
1.61
1.67
1.77
1.73
1.67
1.68
1.67
Cosponsorship in the Senate
Congress
Senate
93rd
94th
95th
96th
97th
98th
99th
100th
101st
102nd
103rd
104th
105th
106th
107th
108th
Years
1973-1974
1975-1976
1977-1978
1979-1980
1981-1982
1983-1984
1985-1986
1987-1988
1989-1990
1991-1992
1993-1994
1995-1996
1997-1998
1999-2000
2001-2002
2003-2004
Mean
Mean
“Bills”
“Bills”
Sponsored Cosponsored Mean Cosponsors
by Each Cosponsors
per
Total Total by Each
Mean
Sponsors“Bills” Legislator Legislator per “Bill” Legislator Distance
101
100
102
99
101
101
101
101
100
101
101
102
100
102
101
100
5123
4913
4722
4188
9674
11228
7596
7782
7370
7686
5824
8101
7001
8265
8745
7804
51
49
45
41
96
111
75
77
74
75
58
79
70
81
87
78
153
137
121
135
219
294
324
361
376
335
232
176
212
290
261
285
3
3
3
3
2
3
4
5
5
4
4
2
3
4
3
4
54
52
49
54
68
77
75
83
82
79
70
59
67
76
71
72
1.46
1.48
1.51
1.46
1.31
1.24
1.24
1.17
1.17
1.21
1.30
1.41
1.33
1.24
1.30
1.27
Mutual Cosponsorship Relations
Congress
93rd
94th
95th
96th
97th
98th
99th
100th
101st
102nd
103rd
104th
105th
106th
107th
108th
Any Bill
House Senate
0.17
0.23
0.17
0.25
0.17
0.21
0.12
0.12
0.14
0.17
0.15
0.16
0.14
0.19
0.18
0.18
0.15
0.17
0.15
0.26
0.17
0.19
0.16
0.20
0.16
0.19
0.16
0.17
0.17
0.17
0.18
0.18
Total Number of Bills
House
Senate
0.23
0.39
0.20
0.34
0.19
0.33
0.15
0.26
0.22
0.27
0.23
0.36
0.21
0.34
0.25
0.39
0.24
0.39
0.14
0.30
0.23
0.34
0.21
0.29
0.24
0.36
0.25
0.37
0.29
0.47
0.34
0.43
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





Total number of bills sponsored by j and cosponsored by i


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
More bills in common = stronger relationship
Weighted cosponsorship distance
wij = å aij c
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 min d kj , dki + dij
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
Congress
House
93rd
94th
95th
96th
97th
98th
99th
100th
101st
102nd
103rd
104th
105th
106th
107th
108th
Best Connected Legislator
0.44
0.57
0.60
0.31
0.27
0.27
0.26
0.25
0.28
0.27
0.22
0.24
0.22
0.28
0.24
0.28
Koch, Edward [D-NY-18]
Pepper, Claude [D-FL-14]
Pepper, Claude [D-FL-14]
Pepper, Claude [D-FL-14]
Montgomery, G. [D-MS-3]
Roe, Robert A. [D-NJ-8]
Breaux, John [D-LA-7]
Waxman, Henry A. [D-CA-29]
Stark, Fortney Pete [D-CA-9]
Fawell, Harris W. [R-IL-13]
Waxman, Henry A. [D-CA-29]
Traficant, James [D-OH-17]
Gilman, Benjamin [R-NY- 20]
McCollum, Bill [R-FL-8]
Young, Don [R-AK]
Saxton, Jim [R-NJ-3]
Strongest Sponsor / Cosponsor Relation
Relationship
69
72
51
58
29
30
16
57
23
14
8
7
7
10
11
14
Commerce Chair, Ranking Member
Armed Services Chair, Ranking Member
Armed Services Chair, Ranking Member
Armed Services Chair, Ranking Member
Armed Services Chair, Ranking Member
Armed Services Chair, Ranking Member
Veterans Affairs Chair, Ranking Member
Veterans Affairs Chair, Ranking Member
Contiguous Districts
Courts and Intellectual Property Chair, Ranking Member
Courts and Intellectual Property Chair, Ranking Member
Courts and Intellectual Property Chair, Ranking Member
Contiguous Districts
Transportation Chair, Ranking Member
(Nearly) Contiguous Districts, Repub. Study Committee
House Administration Chair, Ranking
Staggers, Harley [D-WV-2] / Devine, Samuel [R-OH-12]
Price, Melvin [D-IL-21] / Wilson, Robert [R-CA-41]
Price, Melvin [D-IL-21] / Wilson, Robert [R-CA-41]
Price, Melvin [D-IL-21] / Wilson, Robert [R-CA-41]
Price, Melvin [D-IL-21] / Dickinson, William [R-AL-2]
Price, Melvin [D-IL-21] / Dickinson, William [R-AL-2]
Montgomery, G. [D-MS-3] / Hammerschmidt, J. [R-AR-3]
Montgomery, G. [D-MS-3] / Solomon, Gerald [R-NY-24]
Schulze, Richard T. [R-PA-5] / Yatron, Gus [D-PA-6]
Hughes, William [D-NJ-2] / Moorhead, Carlos [R-CA-22]
Hughes, William [D-NJ-2] / Moorhead, Carlos [R-CA-27]
Moorhead, Carlos [R-CA-27] / Schroeder, Pat [D-CO-1]
Ensign, John E. [R-NV-1] / Gibbons, Jim [R-NV-2]
Shuster, Bud [R-PA-9] / Oberstar, James L. [D-MN-8]
DeMint, Jim [R-SC-4] / Myrick, Sue [R-NC-9]
Ney, Robert W. [R-OH-18] / Larson, John B. [D-CT-1]
Results for the Senate
Congress
Senate
93rd
94th
95th
96th
97th
98th
99th
100th
101st
102nd
103rd
104th
105th
106th
107th
108th
Best Connected Legislator
0.94
1.12
0.90
0.84
0.91
1.28
1.37
1.46
1.39
1.23
1.20
1.58
1.36
1.36
1.61
1.43
Jackson, Henry [D-WA]
Moss, Frank [D-UT]
Dole, Robert J. [R-KS]
Dole, Robert J. [R-KS]
Heinz, Henry [R-PA]
Hatch, Orrin G. [R-UT]
Thurmond, Strom [R-SC]
Cranston, Alan [D-CA]
Kennedy, Edward M. [D-MA]
Mitchell, George J. [D-ME]
Mitchell, George J. [D-ME]
Dole, Robert J. [R-KS]
McCain, John [R-AZ]
Hatch, Orrin G. [R-UT]
Feingold, Russell D. [D-WI]
McCain, John [R-AZ]
Strongest Sponsor / Cosponsor Relation
65
139
33
24
34
63
109
70
77
179
59
38
40
104
53
50
Magnuson, Warren [D-WA] / Cotton, Norris [R-NH]
Jackson, Henry [D-WA] / Fannin, Paul [R-AZ]
Inouye, Daniel [D-HI] / Matsunaga, Spark [D-HI]
Byrd, Robert [D-WV] / Baker, Howard [R-TN]
Inouye, Daniel [D-HI] / Matsunaga, Spark [D-HI]
Baker, Howard [R-TN] / Byrd, Robert [D-WV]
Cranston, Alan [D-CA] / Wilson, Pete [R-CA]
Byrd, Robert [D-WV] / Dole, Robert J. [R-KS]
Mitchell, George J. [D-ME] / Dole, Robert J. [R-KS]
Mitchell, George J. [D-ME] / Sasser, Jim [D-TN]
Mitchell, George J. [D-ME] / Dole, Robert J. [R-KS]
Dole, Robert J. [R-KS] / Daschle, Thomas A. [D-SD]
Lott, Trent [R-MS] / Daschle, Thomas A. [D-SD]
Hutchison, Kay Bailey [R-TX] / Brownback, Sam [R-KS]
McCain, John [R-AZ] / Gramm, Phil [R-TX]
Frist, Bill [R-TN] / Daschle, Thomas A. [D-SD]
Relationship
Commerce Chair, Ranking Member
Interior and Insular Affairs Chair, Ranking Member
Same State
Majority, Minority Leader
Same State
Majority, Minority Leader
Same State
Majority, Minority Leader
Majority, Minority Leader
Federal Housing Reform
Majority, Minority Leader
Majority, Minority Leader
Majority, Minority Leader
Marriage Penalty Relief and Bankruptcy Reform
Personal
Majority, Minority Leader
Quality of Strongest Weighted Relationships

Institutional Ties



Regional Ties



From the same state
In the House they are often from contiguous districts
Issue Ties




House committee chairs and ranking members
Senate majority and minority leaders
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
(si, sj)
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,
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