--- [email protected] wrote:
> I have a question on Mill's ratio and Heckman procedure. When I use
> Mill ratio to take into account the possible endogeneity of one of my
> explanatory variable, I get different result from what I get by using
> regular IV. What can be the resaon (reasons) for that? The more basic
> question is that what distinguishes using Mill ratio and regular IV?
The typical example for -heckman- is wages of women: first a woman has
to decide whether or not to work and than her wage is determined. So
the distribution of wage is rather strange: a spike at zero and than a
normal (though non-Gaussian) right skewed income distribution.
-heckman- often uses instrumental variables to help identify the model,
though strictly speaking that is not necesary. Instrumental can also be
used to solve other problems.
Hope this helps,
Maarten
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
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