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On the Validity of Season of Birth as an Instrument in Wage Equations: A Comment on Angrist & Krueger's "Does Compulsory School Attendance Affect Scho


  • John Bound
  • David A. Jaeger


In an important and provocative paper, `Does Compulsory School Attendance Affect Schooling and Earnings?', Angrist and Krueger use quarter of birth as an instrument for educational attainment in wage equations. To support a causal interpretation of their estimates, they argue that compulsory school attendance laws alone account for the association between quarter of birth and earnings. In this note we present evidence that the association between quarter of birth and earnings is too strong to be fully explained by compulsory school attendance laws in the samples studied by Angrist and Krueger. Moreover, while the association between quarter of birth and educational attainment was weaker for more recent cohorts, we found no evidence that the strength of the relationship between quarter of birth and earnings was also weaker in those cohorts. In addition, we present evidence that suggests the association between quarter of birth and earnings or other labor market outcomes existed for cohorts that were not bound by compulsory school attendance laws. Our results call into question the validity of any causal inferences based on Angrist and Krueger's estimates regarding the effect of education on earnings.

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  • John Bound & David A. Jaeger, 1996. "On the Validity of Season of Birth as an Instrument in Wage Equations: A Comment on Angrist & Krueger's "Does Compulsory School Attendance Affect Scho," NBER Working Papers 5835, National Bureau of Economic Research, Inc.
  • Handle: RePEc:nbr:nberwo:5835
    Note: LS

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    References listed on IDEAS

    1. Imbens, G. & Angrist, J.D., 1992. "Average Causal Response with Variable Treatment Intensity," Harvard Institute of Economic Research Working Papers 1611, Harvard - Institute of Economic Research.
    2. White, Halbert, 1980. "A Heteroskedasticity-Consistent Covariance Matrix Estimator and a Direct Test for Heteroskedasticity," Econometrica, Econometric Society, vol. 48(4), pages 817-838, May.
    3. Solon, Gary, 1992. "Intergenerational Income Mobility in the United States," American Economic Review, American Economic Association, vol. 82(3), pages 393-408, June.
    4. Joshua D. Angrist & Alan B. Keueger, 1991. "Does Compulsory School Attendance Affect Schooling and Earnings?," The Quarterly Journal of Economics, Oxford University Press, vol. 106(4), pages 979-1014.
    5. Griliches, Zvi, 1977. "Estimating the Returns to Schooling: Some Econometric Problems," Econometrica, Econometric Society, vol. 45(1), pages 1-22, January.
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    JEL classification:

    • J24 - Labor and Demographic Economics - - Demand and Supply of Labor - - - Human Capital; Skills; Occupational Choice; Labor Productivity


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