[Limdep Nlogit List] Simulating unconditional WTP

Damien Jourdain djourdain at ait.asia
Wed Apr 4 00:56:50 AEST 2018


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



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