One Congress at a Time DW-NOMINATE (Nokken-Poole)
Updated 1 June 2015
Below are the legislator coordinate files from a One-Congress-at-a-Time DW-NOMINATE scaling
developed by Nokken and Poole (Nokken, Timothy P. and Keith T. Poole. 2004.
"Congressional Party Defection in American History." Legislative
Studies Quarterly, 29:545-568, 2004). The aim is to allow the maximum amount
of movement of legislators from Congress to Congress. First, the DW-NOMINATE two-dimensional
constant coordinate model, that is, every legislator has the same ideal point throughout
his or her career in the two dimensional space, is run to convergence. Second, holding the
roll call outcomes from the two dimensional constant model fixed, an ideal point for every
legislator in every Congress is estimated. Changes in ideal points of members from Congress
to Congress can then be analyzed against the background of the fixed cutting lines.
Nokken and Poole used this method to compare party switchers to members who did not switch
parties between any pair of Congresses.
If you use the second dimension be sure to multiply it by the weight. For the House the weight is
0.3988 and for the Senate the weight is 0.5638.
The format of the legislator files is:
1. Congress Number
2. ICPSR ID Number: 5 digit code assigned by the ICPSR as
corrected by Howard Rosenthal and myself.
3. State Code: 2 digit ICPSR State Code.
4. Congressional District Number (0 if Senate)
5. State Name
6. Party Code: 100 = Dem., 200 = Repub. (See PARTY3.DAT)
8. 1st Dimension Coordinate
9. 2nd Dimension Coordinate
11. Number of Votes
12. Number of Classification Errors
13. Geometric Mean Probability
House Congress by Congress
Legislator Coordinates: HL01113NP2_2014.DAT (Text File, 37,521 lines)
Senate Congress by Congress
Legislator Coordinates: SL01113NP2_2014.DAT (Text File, 9,063 lines)
NOMINATE Data, Roll Call Data, and Software
Course Web Pages: University of Georgia (2010 - )
Course Web Pages: UC San Diego (2004 - 2010)
University of San Diego Law School (2005)
Course Web Pages: University of Houston (2000 - 2005)
Course Web Pages: Carnegie-Mellon University (1997 - 2000)
Analyzing Spatial Models of Choice and Judgment with R
Spatial Models of Parliamentary Voting
Recent Working Papers
Analyses of Recent Politics
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Bio of Keith T. Poole