Non-random samples have been discusses in microeconometrics after the contribution of Heckman (Ref. 1) in sample selection. Though the above approach has many applications, if there are two layers of selection and the model lumps together two selection rules in to one. This single selection can be misspecified as one has to precede the other. For example in the case of participation and employment of women in the labor market, only those who participate can be considered for selection for employment. Here one has to have a double selection procedure where the participation determines the first selection, and employment becomes the second. Mohanty (Ref. 2) applied a double-selection rule to the wage-equations in their models. This study extends this approach for discrete response variable in the final outcome equation. (28 refs.)
展开▼
