# Re: st: Heckman and Oaxaca

 From daneshva@ccmail.nevada.edu To statalist@hsphsun2.harvard.edu Subject Re: st: Heckman and Oaxaca Date Thu, 28 Oct 2004 07:12:03 -0700

```Natalia,

There is no problem with dummies in a Heckman equation and "decomp."
decomp uses the mean of the variable, in this case the proportion of the
sample with dummy variable equal to one, and multiplies it by the
respective coefficient.  To see the details of the calculations, use can
use "himod, ds" and "lomod, ds."  this will give you the contribution of
each variable to the total endowment and the total residual.

It is possible to get high percentages (-301.0).  It means that the group
that you are using as the "low" or discriminated group actually has
advantage over the "high" group.  The commend, "himod, ds" or "lomod, ds"
will reveal what variables are the cause of high percentages.

Nasser

"Natalia Ferreira"
<nat6672@hotmail.com>             To:      statalist@hsphsun2.harvard.edu
Sent by:                          cc:
owner-statalist@hsphsun2.         Subject: st: Heckman and Oaxaca
harvard.edu

10/27/2004 05:04 p.m.
statalist

Hi everybody

I´m estimating a Heckman wage equation to migrants and not migrants,
and
after all I want to compare them by a Oaxaca decomposition, but I have a
question: there is any problem if my Heckman equation have some dummies?
How
"decomp" command deal with the dummies variables? Does it take means of
zeros
and ones? The results of my "decomp" give me discrimation % of -301.0
(D/R).
The % should not be between 0-100? The results are below:

Summary of decomposition results (as %)
-------------------------------------------
Amount attributable:             |    -10.3
- due to endowments (E):         |      5.2
- due to coefficients (C):       |    -15.5
Shift coefficient (U):           |     11.6
Raw differential (R) {E+C+U}:    |      1.3
Adjusted differential (D) {C+U}: |     -3.9
---------------------------------+---------
Endowments as % total (E/R):     |    401.0
Discrimination as % total (D/R): |   -301.0
-------------------------------------------

Thanks for the help, Natalia B.
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