[Limdep Nlogit List] Simulating unconditional WTP

William Greene wgreene at stern.nyu.edu
Wed Apr 4 01:13:10 AEST 2018


Damien. The simulated coefficients are not correlated because you used
independent random draws to create them.  You should be using rna1 in the
first one, rna1,rna2 in the second one and rna1,rna2,rna3 in the third one.
/B, Greene

On Tue, Apr 3, 2018 at 10:56 AM, Damien Jourdain <djourdain at ait.asia> wrote:

> Dear All,
>
>
>
> I ran the following RPL-EC model. It gives me reasonable results.
>
> ? ML-EC Model
>
> Sample; ALL$
>
> Calc; Ran(12345)$
>
> RPLOGIT
>
>       ; Choices = 1,2,3
>
>       ; Lhs = CHOICE, CSET, ALT
>
>       ; Model:
>
>       U(1)   = A1 + BE*BENEF + LA*LAB + CA*CASH +RI*RISK + FEL*FERTLO +FEH*
> FERTHI /
>
>       U(2,3) =      BE*BENEF + LA*LAB + CA*CASH +RI*RISK + FEL*FERTLO +FEH*
> FERTHI
>
>       ; Fcn =  BE(l), LA(n),  CA(n), RI(n), FEH(n)
>
>       ; Pds = 6
>
>       ; Pts = 20
>
>       ; Shuffled
>
>       ; Correlation
>
>       ; WTP = LA/BE, CA/BE, RI/BE, FEH/BE
>
>       ; ECM = (2,3)
>
>       ; Parameters
>
>       ; Maxit = 300$
>
>
>
>
>
> I have obtained the conditional WTP (using the WTP command) but in fact I
> would like to manipulate simulated un-conditional WTPs. As the coefficients
> are correlated, I understand that I have to use the Cholesky decomposition
> (provided in the model output) to be able to draw correlated random
> coefficients. I have two set of questions:
>
>
>
> First, can I use the WALD command to develop these simulations (I know this
> can be done with an MNL model, but I do not see any simple manner to use
> the
> B and VARB matrices obtained from the model for a RPL model.
>
>
>
> Second, as I assumed that I could not use WALD, I developed the following
> commands for simulating the first three random coefficients:
>
>
>
> SAMPLE; 1-1000$
>
> create
>
> ; rna1 = rnn(0,1)
>
> ; rna2 = rnn(0,1)
>
> ; rna3 = rnn(0,1)
>
> ; rna4 = rnn(0,1)
>
> ; rna5 = rnn(0,1)
>
> ; rna6 = rnn(0,1)
>
> ; MUBEN = B(1) + B(8)  * RNA1
>
> ; MULAB = B(2) + B(13) * RNA2 + B(9)  * RNA3
>
> ; MUCAS = B(3) + B(14) * RNA4 + B(15) * RNA5 + B(10) * RNA6
>
> $
>
>
>
> (the coefficients are correct and correspond to the Cholesky matrix
> coefficients )
>
>
>
> When checking the simulated coefficients, I can reproduce the coefficients
> mean and standard deviation, but they are not correlated as I had expected
> given that I used the Cholesky coefficients to reproduce these correlations
>
>
>
> I do not understand what I have done wrong?
>
>
>
> Any help is welcomed.
>
>
>
>
>
>
>
> Damien
>
>
>
>
>
>
>
>
>
> DSTAT; RHS = MUBEN, MULAB, MUCAS; out=2$
>
> --------+---------------------------------------------------
> ----------------
> --
>
>         |                  Standard
> Missing
>
> Variable|         Mean    Deviation      Minimum      Maximum    Cases
> Values
>
> --------+---------------------------------------------------
> ----------------
> --
>
>    MUBEN|      -3.7348      .408152    -5.023775    -2.357132     1000
> 0
>
>    MULAB|      -.02753      .028474     -.117069      .048933     1000
> 0
>
>    MUCAS|     -.015962      .015583     -.064371      .035926     1000
> 0
>
> --------+---------------------------------------------------
> ----------------
> --
>
>
>
> Descriptive Statistics for   3 variables
>
> DSTAT results are matrix LASTDSTA in current project.
>
>
>
> Correlations computed for 3 variables.
>
>
>
> --------+--------------------------
>
> Cor.Mat.|   MUBEN    MULAB    MUCAS
>
> --------+--------------------------
>
>    MUBEN| 1.00000   .04327  -.04466
>
>    MULAB|  .04327  1.00000  -.01857
>
>    MUCAS| -.04466  -.01857  1.00000
>
>
>
>
>
> I am really far off the model outputs
>
> --------+--------------------------------------------
>
> Cor.Mat.|     ONE       LA       CA       RI      FEH
>
> --------+--------------------------------------------
>
>      ONE| 1.00000  -.61706  -.83717   .07331  -.06425
>
>       LA| -.61706  1.00000   .23113  -.52217  -.23501
>
>       CA| -.83717   .23113  1.00000   .09078  -.16867
>
>       RI|  .07331  -.52217   .09078  1.00000   .63762
>
>      FEH| -.06425  -.23501  -.16867   .63762  1.00000
>
>
>
>
>
>
>
>
>
>
>
>
>
> Dr. Damien Jourdain
>
> Agricultural and Natural Resources Economist
>
> Visiting Assistant Professor
>
> Asian Institute of Technology / CIRAD G-EAU
>
> Natural Resource Management / Water Engineering and Management
>
> _______________________________________________
> Limdep site list
> Limdep at mailman.sydney.edu.au
> http://limdep.itls.usyd.edu.au
>
>


-- 
William Greene
Department of Economics
Stern School of Business, New York University
44 West 4 St., 7-90
New York, NY, 10012
URL: https://protect-au.mimecast.com/s/YjmXCD1jy9twjlkLTWn5pG?domain=people.stern.nyu.edu
Email: wgreene at stern.nyu.edu
Ph. +1.212.998.0876
Editor in Chief: Journal of Productivity Analysis
Editor in Chief: Foundations and Trends in Econometrics
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