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From |
Austin Nichols <austinnichols@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: heckman selection model with endogenous covariates |

Date |
Thu, 8 Apr 2010 09:48:45 -0400 |

James <James.Rao@agr.uni-goettingen.de> : The selection model estimated via MLE (or a hurdle model using equations like you have given below; since you don't specify errors or their distributions, or true functional forms, the equations do not actually dictate an estimator) requires very strong distributional assumptions; if you are willing instead to assume that E(labor|X) = exp(Xb)v with v a mean one error that may also be zero (e.g. gamma distributed or some mixture), then you have a GLM model that looks like -poisson- and can be estimated with that command. I.e. it looks like ln(labor) = Xb + e when labor>0 but allows labor=0 as well. If you assume that a column of X is endogenous, but you have an instrument, you can use a GMM version of that model; see the help file for -ivpois- on SSC or the new -gmm- command in Stata 11. http://fmwww.bc.edu/repec/bocode/i/ivpois.html http://www.stata.com/help.cgi?gmm On Thu, Apr 8, 2010 at 5:13 AM, Rao, James <James.Rao@agr.uni-goettingen.de> wrote: > Dear users, > > Am interested in estimating a lbor demand equation as follows: > > ln_labor=alpha + b1_X + b2_treatment > > Since some respondents do not use hired labor, i specify the probability of > using hired labor as: > > prob(labor)=b3_Z + b4_treatment > > and then estimate the two equations jointly following heckman selection > approach. > > My concern is that the treatment variable in both equations is potentially > endogenous. Anyone with an idea of how I can address this potential > endogeneity within the framework of heckman selection models? > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: heckman selection model with endogenous covariates***From:*"Rao, James" <James.Rao@agr.uni-goettingen.de>

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