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ACKNOWLEDGMENT OF RELATED PRIOR WORK

Published online by Cambridge University Press:  03 November 2006

Jeffrey M. Wooldridge
Jeffrey M. Wooldridge
Affiliation:
Michigan State University Address correspondence to Jeffrey M. Wooldridge, Department of Economics, Michigan State University, East Lansing, MI 48824-1038, USA; e-mail: wooldri1@msu.edu
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Extract

In Wooldridge (2005), I posed a problem whose solution involved showing that the so-called ignorability of treatment assumption, commonly used in the treatment effects literature, was necessarily violated. In particular, in a setting with multiple treatment effects and without distributional or functional form assumptions, I assumed that treatment was randomized with respect to the counterfactual outcomes but not with respect to the covariates. I applied the law of iterated expectations to provide a simple proof that ignorability (given the covariates) necessarily fails.

Type
MISCELLANEA
Information
Econometric Theory , Volume 22 , Issue 6 , December 2006 , pp. 1177 - 1178
Copyright
© 2006 Cambridge University Press

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References

REFERENCES

Heckman, J. & S. Navarro-Lozano (2004) Using matching, instrumental variables, and control functions to estimate economic choice models. Review of Economics and Statistics 86, 30–57.CrossRefGoogle Scholar
Rosenbaum, P. (1984) The consequences of adjusting for a concomitant variable that has been affected by treatment. Journal of the Royal Statistical Society, Series A 147, 656–666.CrossRefGoogle Scholar
Wooldridge, J.M. (2005) Violating ignorability by controlling for too many factors. Econometric Theory 21, 1026–1028.CrossRefGoogle Scholar