Heckman两阶段

HeckmanSelectionModel赫克曼备择模型赫克曼二阶段备择模型王志刚有几篇关于Heckman备择模型的文章。2()=0=0LRllll为假设时的对数似然函数的最大值；为未假设的对数似然函数的最大值。select(...)specifiesthevariablesandoptionsfortheselectionequation.ItisanintegralpartofspecifyingaHeckmanmodelandisrequired.Theselectionequationshouldcontainatleastonevariablethatisnotintheoutcomeequation.Ifdepvar_sisspecified,itshouldbecodedas0or1,with0indicatinganobservationnotselectedand1indicatingaselectedobservation.Ifdepvar_sisnotspecified,observationsforwhichdepvarisnotmissingareassumedselected,andthoseforwhichdepvarismissingareassumednotselected.TheStatapackagehastwocomponents:theexecutableandtheado-files..updateexecutable,force.updateado,forceHeckmanlweducationagechildren,select(agemarriedchildreneducation)nologSTATA对大小写敏感。Heckmanlweducationagechildren,select(w=agemarriedchildreneducation)nologBDCEND