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# Re: st: Double Selection - Mill's ratios computation

 From Nick Cox To "statalist@hsphsun2.harvard.edu" Subject Re: st: Double Selection - Mill's ratios computation Date Thu, 12 Dec 2013 23:20:42 +0000

```Please note http://www.stata.com/statalist/archive/2006-08/msg00432.html

Nick
njcoxstata@gmail.com

On 12 December 2013 19:56, Fabrizio Colella - 1348010
<colella.fabrizio@studbocconi.it> wrote:
> Dear all,
>
> I am performing an Oaxaca Blinder wage decomposition among women working part-time and women working full-time,
> with a double switching model as selection-correction.
>
> To do that I performed first two -probit- regressions to "correct" for two types of selection:
> 1) participation vs. non-participation in the labor market
> 2) full-time vs. part-time – (CONDITIONAL ON PARTICIPATION)
> I calculated the two mills ratios and I used them as covariates in the –oaxaca-.
>
> As you know there are many different methods to control for selection using the inverse Mill's ratios (Heckman, Greene, Maddala),
> Below there is the code I am using, anyway I am not sure it works. Please, could anybody check it?
>
> **************************************
> *** Selection
> probit labor_force_partecipation age_25_35 … … health_prob, robust iterate(10)
> predict Xb1 , xb
> gen mills1 = .
> replace mills1 = normalden(-Xb1)/(1-(normal(-Xb1))) if lfp==1 //workers
> probit part_time age_25_35 … … health_prob, robust iterate(10)
> predict Xb2 , xb
> gen mills2 = .
> replace mills2 = normalden(-Xb2)/(1-(normal(-Xb2))) if part_full_only==1 //part_timers
> replace mills2 = -normalden(-Xb2)/((normal(-Xb2))) if part_full_only==0 //full_timers
> *** OB decomposition ***
> oaxaca ln_hourly_wage ed_primary … … worker mills1 mills2 [pweight=pb040], by(part_full_only) weight(0)
> *******************************
>

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