In a recent, and widely cited, paper, Ashenfelter and Krueger (1994) use a new sample of identical
twins to investigate the contribution of genetic ability to the observed cross-sectional return to schooling.
This paper re-examines Ashenfelter and Krueger’s estimates using three additional years of the same twins
survey. I find that the return to schooling among identical twins is about 10 percent per year of schooling
completed. Most importantly, unlike the results reported in Ashenfelter and Krueger, I find that the within-
twin regression estimate of the effect of schooling on the log wage is smaller than the cross-sectional
estimate, implying a small upward bias in the cross-sectional estimate. Ashenfelter and Krueger’s
measurement error corrected estimates are insignificantly different from those presented here, however.
Finally, there is evidence of an important individual-specific component to the measurement error in
schooling reports.

Year of Publication
Date Published
Publication Language
Citation Key
Economics of Education Review, Vol. 18, 1999
Rouse, C. (1997). Further Estimates of the Economic Return to Schooling from a New Sample of Twins. Retrieved from (Original work published July 1997)
Working Papers