set memory 30m
set more off

log using heckman_treatment.log, replace

*** Heckman Selection Models

use http://www.stata-press.com/data/r8/womenwk, clear
generate d = 1
replace  d = 0 if wage == .

heckman wage educ age, select (married children educ age) twostep
heckman wage educ age, select (married children educ age) nolog

*heckman wage educ age, select (d = married children educ age) twostep nolog
*probit d  married children educ age, nolog

predict cndwage, ycond
summarize wage cndwage if wage < .

predict expwage, yexpected
gen wage0 = wage
replace wage0 = 0 if wage >= .
summarize wage0 expwage 


*** Heckprob 

use http://www.stata-press.com/data/r8/school, clear

* vote = 1 if someone voted for increase in property taxes
* private = 1 if children attend prive school

tab private vote
heckprob private years logptax, sel (vote = years loginc logptax) nolog
heckprob private years logptax, sel (vote = years loginc logptax) robust nolog



*** Treatment effects model

use http://www.stata-press.com/data/r8/labor, replace
generate wc = 0
replace wc = 1 if we > 12
tab wc
regress ww wa cit wc

treatreg ww wa cit, treat(wc = wmed wfed) twostep nolog
predict wwctrt, yctrt
predict wwcntrt, ycntrt
generate diff = wwctrt - wwcntrt
summarize diff
ttest wwctrt = wwcntrt, unequal unpaired

drop wwctrt wwcntrt diff

treatreg ww wa cit, treat(wc = wmed wfed) nolog
predict wwctrt, yctrt
predict wwcntrt, ycntrt
generate diff = wwctrt - wwcntrt
summarize diff
ttest wwctrt = wwcntrt, unequal unpaired