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Sample selection bias as a speciation error

Publication Source

Heckman, J.J. 1978

Publication Title

Econometrica

Publication Type

Journal article

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Abstract

This paper discusses the bias that results from using nonrandomly selected samples to estimate behavioral relationships as an ordinary specification error or "omitted variables" bias. A simple consistent two stage estimator is considered that enables analysts to utilize simple regression methods to estimate behavioral functions by least squares methods. The asymptotic distribution of the estimator is derived.