RE: st: Oaxaca decomposition for Tobit

[Marco Ercolani <m.g.ercolani@bham.ac.uk>]

Dear Statalisters,

1. Thank you to Farida for his suggestions. In particular I am keen to know the reasons why the "detailed variable decompositions" are unstable. I teach (aggregate) Oaxaca decompositions so I am interested in specific references on this problem. My research decompositions use a moderately large number of observations, 200,000 to 2,000,000 and the "detailed variable decompositions" appear to work quite well and the results make sense. Perhaps the problem is just one of degrees of freedom? Or is it something else? Please let me know.

2. Thank you to Maarten for moderating our excesses. I work among economists and I am therefore used to a daily discordant tone. In time I have become tone deaf ;-)

3. I would still like to hear from anyone who knows how to deal with my technical questions of how to carry out the detailed Blinder-Oaxaca decomposition for Tobit in Stata. In particular I would like to know if the multitude of marginal effects in Tobit creates problems.

All the best,
 Marco.



Dr Marco G. Ercolani
 Senior Undergraduate Tutor
Department of Economics
University of Birmingham
Edgbaston, B15 2TT

________________________________________
From: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] On Behalf Of FARIDA HUSNA [faridahusna2001@gmail.com]
Sent: 17 January 2011 20:30
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: Oaxaca decomposition for Tobit

Marco,

You are not supposed to report for each variable.  They are unstable
and not worth looking.  The experts in the field of discrimination -
Blau, Oaxaca, Cotten, Blinder, Neumark, Khan, Polachek, Reimer,
Goldin, O Neill - do not report them.

The output created by "oaxaca.ado" is useless.  It was written by Ben
Jann.  He is making outlandish claims on how to do this but he is not
expert in this field.  "nldecompose.ado" is by Sinning, Hahn, and
Bauer.  Two of them are active researchers in the filed of gender
discrimination.  You should go back to "nldecompose.ado"

Cheers,

FARIDA

On Mon, Jan 17, 2011 at 10:59 AM, Marco Ercolani
<m.g.ercolani@bham.ac.uk> wrote:
>
> Dear All,
>
> I wish to carry out detailed Blinder-Oaxaca variable-level decompositions for a Tobit regression. Can anyone suggest a useful "ado" script?
>
> I have been using the excellent "oaxaca.ado" by Ben Jann but this does not accommodate tobit estimation. "oaxaca.ado" is excellent because it includes detailed decompositions for each variable and it will automatically bootstrap the confidence intervals.
>
> I also know that the very good "nldecompose.ado" can cope with Tobit but it does not provide individual variable decompositions.
>
> A very old version of oaxaca.do did seem to work for Tobit because it used stored estimates to carry out the decompositions but this version no longer exists.
>
> I suspect the problem is that in Tobit we can define more than one marginal effect per variable and it is therefore not obvious which marginal effect to choose when carrying out the Blinder-Oaxaca decomposition.
>
> I'd be grateful for any suggestions.
>
> Yours,
>  Marco.
>
>
> Dr Marco G. Ercolani
> Department of Economics
> University of Birmingham
> Edgbaston, B15 2TT
>
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