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From |
fatma bircan <bircan@metu.edu.tr> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Heckman comand sample issue |

Date |
Wed, 21 Apr 2004 15:20:08 +0300 |

Why not replace ln wages =0 when they are missing. You should also define a binary variable which takes the value of 1 when the person is a wage earner and zero otherwise. In your case ilf=1 if there is labor force participation and ilf=0 if otherwise. Check also other variables for missing values. To consider the whole sample you should replace them with zero in case they have missing values. Goodluck! ------------------- >Dear Statalist users, > >please excuse if this is a basic question, however, I could not find the >answer or the right search terms to find it in the archives. >I have a data set with about 600,000 observations, of which about 90,000 >are wage earners. In it, I would like to run the heckman command to >correct for sample selectivity bias. My earnings variable is ln(wages), >and thus has missing values for all observations that do not have a >recorded wage. Hence, if I run my heckman with: > >Heckman ln_wages varlist1, sel(ilf = varlist1 varlist2), > >where varlist2 are my exclusion restrictions and ilf is a participation >dummy, the number of observations comes down to 90,000 (ilf does not >only take the value of 1, since I failed to clean the data completely, >yet). >My aim is to run the selection function on the whole sample (of 600,000 >obs), and to get stata to run the wage function without the missing >observations. The only solution I found was to replace all missing >values with -9999 in ln_wages. > >Is there some better way to tell stata to use the whole sample for the >selection function, even if ln_wages is missing? > >Thank you very much in advance for your help. > >Nicolas > >* >* For searches and help try: >* http://www.stata.com/support/faqs/res/findit.html >* http://www.stata.com/support/statalist/faq >* http://www.ats.ucla.edu/stat/stata/ > Fatma Bircan Middle East Technical University Department of Economics 210-2032 xxxxxxxxxxxxxxxxxxxxxxxxxxxxx * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Heckman comand sample issue***From:*"Nicolas Theopold" <Nicolas.Theopold@economics.oxford.ac.uk>

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