W-NOMINATE Parametric Bootstrap Program Page

LEGACY CONTENT. If you are looking for Voteview.com, PLEASE CLICK HERE

This site is an archived version of Voteview.com archived from University of Georgia on May 23, 2017. This point-in-time capture includes all files publicly linked on Voteview.com at that time. We provide access to this content as a service to ensure that past users of Voteview.com have access to historical files. This content will remain online until at least January 1st, 2018. UCLA provides no warranty or guarantee of access to these files.

W-NOMINATE Parametric Bootstrap Program

Jeff Lewis and Keith Poole

(Updated 24 October 2006)

W-NOMINATE is a scaling procedure that performs parametric unfolding of binary choice data. Given a matrix of binary choices by individuals (for example, Yes or No) over a series of Parliamentary votes, W-NOMINATE produces a configuration of legislators and outcome points for the Yea and Nay alternatives for each roll call using a probabilistic model of choice. It is discussed in detail in:

"Measuring Bias and Uncertainty in Ideal Point Estimates via the Parametric Bootstrap"

Jeffrey B. Lewis

Keith T. Poole

Spatial Models of Parliamentary Voting

Congress: A Political-Economic History of Roll Call Voting

American Journal of Political Science

Please read the documentation on how to use the W-NOMINATE program on the W-NOMINATE page before continuing below. The Parametric Bootstrap program is a slightly modified version of W-NOMINATE and the input and output files are, with two minor exceptions, exactly the same. The documentation below concentrates on the two differences and complements the discussion on the W-NOMINATE page.

Examples

107^th Senate (Detailed Discussion of Input and Output Files)

96^th House

Example One: The 107^th Senate.

Parametric Bootstrap W-NOMINATE

^th

W-NOMINATE Parametric Bootstrap Scaling Program Executable (Compiled For WINTEL Machines -- WNOMJLEWIS_NO_OC.EXE)

W-NOMINATE Parametric Bootstrap Program Source Code (FORTRAN -- WNOMJLEWIS_NO_OC.FOR)

Control Card File (NOMSTART_JLEWIS.DAT)

107^th Senate Roll Call Data (SEN107KH.ORD)

Plot_Boostrap_S107.R

NOMSTART_JLEWIS.DAT


SEN107KH.ORD               Data File Name -- can include path statement
NOMINAL MULTIDIMENSIONAL UNFOLDING OF 107th SENATE  Title of Run
  633   10   18            Number RCs, Left on 1st, Up on 2nd
    2   36 1001            Number Dimensions, Number Characters to Read From Header, Number of Bootstrap Trials
 15.0000  0.5000           Starting Values for BETA and WEIGHT
  0.0250   20              RC Min. Cutoff, Number RCs for Legislator
(36A1,3600I1)              Format for Roll Call File
(1X,I4,36A1,1X,4I4,51F7.3) Format for Legislator Coordinate File -- NOM31.DAT
(1X,I4,36A1,80F10.4)       Format for W-NOMINATE, H-S, and Metric Coordinate File -- NOM36.DAT -- 
                           and FORT.26 -- The Parametric Bootstrap Legislator Coordinates and Standard Errors

Lines one, two, and three are the same as the example posted on the W-NOMINATE Page.
The fourth line, in order, is the number of dimensions, the number of characters to read of the front of each legislator's record ("36" for the 107^th Senate -- this number can be set as high as 99 depending upon how you have organized your data -- contact Keith Poole KPoole@ucsd.edu if you have questions about how to do this), and the number of parametric bootstrap trials.

Technically, the computer "sees" the third and fourth lines as:
```
006330001000018
and
000020003601001
```
This spacing must not be changed! If you want to analyze 1221 roll calls in 3 dimensions with everything else the same the two lines must look like this:
```
012210001000018
000030003601001

or with the zeroes removed

 1221   10   18
    3   36 1001
```
Although in this setup we have the number of bootstrap trials set to 1001 we recommend that the user set this to either 11 or 6 (00011 or 00006) initially and study the output files before doing a large number of trials.
The Fifth, sixth, seventh, and eighth lines are the same as the example posted on the W-NOMINATE Page.

WNOMJLEWIS_NO_OC

NOM21.DAT

NOM23.DAT

NOM31.DAT

NOM33.DAT

NOM36.DAT

FORT.26

NOM21.DAT, NOM23.DAT, NOM31.DAT, NOM33.DAT, and NOM36.DAT

The format of these files is explained in detail on the W-NOMINATE Program page. However, each file has all the bootstrap runs stacked upon one another. For example, the NOM21.DAT file as the initial output exactly like W-NOMINATE. This output is then repeated for each of the bootstrap trials.

For example, for the legislator coordinate output file -- NOM31.DAT -- if there are 102 Senators and 1001 bootstrap trials, then there will be 102,102 lines in the file.

FORT.26

FORT.26 has the W-NOMINATE legislator coordinates and the bootstrapped standard errors. If the number of trials is set to 1001, then the number of bootstrap draws is 1000 (or always one less than the number). The extra "1" is the inital W-NOMINATE scaling to obtain the choice probabilities for the parametric bootstrap trials (see our Political Analysis articles for the details).

The file with the bootstrapped standard errors for the 107^th Senate looks something like this (these are random draws so your results may be slightly different):


   1 1079991099 0USA     20000BUSH           0.7605    0.1849    0.8266    0.1409    0.1312    0.3363    1.0000   -0.0440   -0.0440    1.0000
   2 1074970041 0ALABAMA 20001SESSIONS       0.6413   -0.4361    0.6926   -0.4954    0.0758    0.1152    1.0000    0.0533    0.0533    1.0000
   3 1079465941 0ALABAMA 20001SHELBY         0.5048   -0.1749    0.5646   -0.2032    0.0784    0.1246    1.0000    0.0532    0.0532    1.0000
   4 1071490781 0ALASKA  20001MURKOWSKI      0.6319    0.4609    0.6786    0.4407    0.0707    0.1546    1.0000    0.0646    0.0646    1.0000
   5 1071210981 0ALASKA  20001STEVENS        0.5176    0.3038    0.5899    0.3249    0.0887    0.1598    1.0000    0.0395    0.0395    1.0000
                                  etc etc etc
         The first column is an integer counter
         The column in red is the Congress number
         The column in blue is the ICPSR ID Number
         The column in Magenta is the ICPSR State Code
         The column of zeroes will show the two digit Congressional District Number for House Roll Call Matrices
         The column in Coral is the first seven letters of the State Name
         The column in Midnightblue is the party code -- see the Party Codes Page for a complete listing
         The column in Firebrick are the ICPSR Occupancy and Election Codes
         Name of Senator/Representative
         The columns in Turquoise are the W-NOMINATE Coordinates. 
         The columns in Purple are the Mean Coordinate Values For the 1000 Trials
         The columns in Green are the Parametric Bootstrapped Standard Errors
         The last four columns are the Pearson Correlation Matrix between the two dimensions.  The column
           in Deeppink is the Pearson Correlation Between the First and
                  Second Dimension Coordinate estimates across the 1000 Bootstrap Trials
                  This can be used to obtain the corresponding covariance term
                                  etc etc etc
  98 1071492256 0WEST VI 10001ROCKEFELLER   -0.7407   -0.1129   -0.7197   -0.1616    0.0551    0.1440    1.0000   -0.0500   -0.0500    1.0000
  99 1074930925 0WISCONS 10001FEINGOLD      -0.7206   -0.6933   -0.7128   -0.6586    0.0497    0.0739    1.0000   -0.3755   -0.3755    1.0000
 100 1071570325 0WISCONS 10001KOHL          -0.5807    0.1534   -0.5395    0.0984    0.0638    0.1491    1.0000    0.0402    0.0402    1.0000
 101 1074970668 0WYOMING 20001ENZI           0.7769    0.3826    0.7873    0.3420    0.0529    0.1471    1.0000    0.1047    0.1047    1.0000
 102 1071563368 0WYOMING 20001THOMAS         0.8422    0.3621    0.8374    0.3115    0.0555    0.1420    1.0000    0.0080    0.0080    1.0000

Example Two: The 96^th House.

Control Card File for 96^th House (NOMSTART_JLEWIS.H96)

96^th House Roll Call Data (HOU96KH.ORD)

Plot_Boostrap_H96.R

NOMSTART_JLEWIS.H96


HOU96KH.ORD                Data File Name -- can include path statement
 NOMINAL MULTIDIMENSIONAL UNFOLDING OF 96TH HOUSE   Title of Run
 1276    1    4            Number RCs, Left on 1st, Up on 2nd
    2   36 1001            Number Dimensions, Number Characters to Read From Header, Number of Bootstrap Trials
 15.0000  0.5000           Starting Values for BETA and WEIGHT
  0.0250   20              RC Min. Cutoff, Number RCs for Legislator
(36A1,15000I1)             Format for Roll Call File
(1x,I4,36A1,1X,4i4,51f7.3) Format for Legislator Coordinate File -- NOM31.DAT
(I4,1X,36A1,80F10.4)       Format for W-NOMINATE, H-S, and Metric Coordinate File -- NOM36.DAT -- 
                           and FORT.26 -- The Parametric Bootstrap Legislator Coordinates and Standard Errors

^th


   1  969990699 0USA     10000CARTER        -0.5675    0.3060   -0.5532    0.2532    0.0613    0.1204    1.0000    0.0202    0.0202    1.0000
   2  961072141 1ALABAMA 20001EDWARDS J      0.2690    0.1142    0.2553    0.1208    0.0352    0.0650    1.0000   -0.0539   -0.0539    1.0000
   3  961071741 2ALABAMA 20001DICKINSON      0.5833    0.2121    0.5709    0.2402    0.0376    0.0787    1.0000    0.0011    0.0011    1.0000
   4  961103741 3ALABAMA 10001NICHOLS        0.1722    0.8014    0.1331    0.8823    0.0536    0.1140    1.0000    0.2858    0.2858    1.0000
   5  961100041 4ALABAMA 10001BEVILL  T     -0.0197    0.9998   -0.0387    0.9896    0.0404    0.0288    1.0000    0.0220    0.0220    1.0000
                                  etc etc etc
         The first column is an integer counter
         The column in red is the Congress number
         The column in blue is the ICPSR ID Number
         The column in Magenta is the ICPSR State Code
         The column of zeroes will show the two digit Congressional District Number for House Roll Call Matrices
         The column in Coral is the first seven letters of the State Name
         The column in Midnightblue is the party code -- see the Party Codes Page for a complete listing
         The column in Firebrick are the ICPSR Occupancy and Election Codes
         Name of Senator/Representative
         The columns in Turquoise are the W-NOMINATE Coordinates. 
         The columns in Purple are the Mean Coordinate Values For the 1000 Trials
         The columns in Green are the Parametric Bootstrapped Standard Errors
         The last four columns are the Pearson Correlation Matrix between the two dimensions.  The column
           in Deeppink is the Pearson Correlation Between the First and
                  Second Dimension Coordinate estimates across the 1000 Bootstrap Trials
                  This can be used to obtain the corresponding covariance term
                                  etc etc etc
 436  961467525 6WISCONS 20002PETRI          0.3170   -0.7953    0.3135   -0.8778    0.0364    0.1007    1.0000   -0.2289   -0.2289    1.0000
 437  961203625 7WISCONS 10001OBEY  D       -0.6867   -0.3093   -0.7381   -0.3129    0.0691    0.0635    1.0000   -0.0703   -0.0703    1.0000
 438  961465525 8WISCONS 20001ROTH  T        0.5172   -0.3872    0.5164   -0.4095    0.0351    0.0735    1.0000   -0.0470   -0.0470    1.0000
 439  961465725 9WISCONS 20001SENSENBRENN    0.6537   -0.6186    0.6562   -0.6479    0.0394    0.0712    1.0000   -0.1445   -0.1445    1.0000
 440  961461168 1WYOMING 20001CHENEY  R      0.5594   -0.1952    0.5585   -0.1939    0.0352    0.0710    1.0000   -0.0249   -0.0249    1.0000

Below is a plot of the member coordinates. The R tokens are Republicans, the S tokens are Southern Democrats (11 states of the Confederacy plus Kentucky and Oklahoma), the D tokens are Northern (Non-Southern) Democrats, and the P is President Carter. The vertical and horizontal lines through each representative's ideal point show the 95 percent confidence intervals for each coordinate of that representative's position. Confidence ellipses are shown for representatives whose first-dimension and second-dimension coordinates have a correlation coefficient greater than 0.30 in absolute value.

Example One: The 107th Senate.

Example Two: The 96th House.

Example One: The 107^th Senate.

Example Two: The 96^th House.