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Older and Wiser? Birth Order and IQ of Young Men

  • Black, Sandra E.


    (University of Texas at Austin)

  • Devereux, Paul J.


    (University College Dublin)

  • Salvanes, Kjell G.


    (Norwegian School of Economics)

While recent research finds strong evidence that birth order affects children’s outcomes such as education and earnings, the evidence on the effects of birth order on IQ is decidedly mixed. This paper uses a large dataset on the population of Norway that allows us to precisely measure birth order effects on IQ using both cross-sectional and within-family methods. Importantly, irrespective of method, we find a strong and significant effect of birth order on IQ, and our results suggest that earlier born children have higher IQs. Our preferred estimates suggest differences between first-borns and second-borns of about one fifth of a standard deviation or approximately 3 IQ points. Despite these large average effects, birth order only explains about 3% of the within-family variance of IQ. When we control for birth endowments, the estimated birth order effects increase. Thus, our analysis suggests that birth order effects are not biologically determined. Also, there is no evidence that birth order effects occur because later-born children are more affected by family breakdown.

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Paper provided by Institute for the Study of Labor (IZA) in its series IZA Discussion Papers with number 3007.

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Length: 27 pages
Date of creation: Aug 2007
Date of revision:
Publication status: published in: CESifo Economic Studies, 2011, 57 (1), 103-120
Handle: RePEc:iza:izadps:dp3007
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References listed on IDEAS
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  1. Sandra E. Black & Paul Devereux & Kjell G. Salvanes, 2007. "From the Cradle to the Labor Market? The Effect of Birth Weight on Adult Outcomes," Working Papers 200718, Geary Institute, University College Dublin.
  2. repec:tpr:qjecon:v:120:y:2005:i:2:p:669-700 is not listed on IDEAS
  3. Alison Booth & Hiau Kee, 2009. "Birth order matters: the effect of family size and birth order on educational attainment," Journal of Population Economics, Springer, vol. 22(2), pages 367-397, April.
  4. repec:oup:qjecon:v:122:y:2007:i:1:p:409-439 is not listed on IDEAS
  5. Hanushek, Eric A, 1992. "The Trade-Off between Child Quantity and Quality," Journal of Political Economy, University of Chicago Press, vol. 100(1), pages 84-117, February.
  6. S Black & Paul Devereux & Kjell Salvanes, 2005. "The More the Merrier? The Effect of Family Size and Birth Order on Childrens Education," CEE Discussion Papers 0050, Centre for the Economics of Education, LSE.
  7. Behrman, Jere R & Taubman, Paul, 1986. "Birth Order, Schooling, and Earnings," Journal of Labor Economics, University of Chicago Press, vol. 4(3), pages S121-45, July.
  8. repec:oup:qjecon:v:120:y:2005:i:2:p:669-700 is not listed on IDEAS
  9. repec:tpr:qjecon:v:122:y:2007:i:1:p:409-439 is not listed on IDEAS
  10. Paul J. Devereux & Sandra E. Black & Kjell G. Salvanes, 2007. "From the cradle to the labor market? The effect of birth weight on adult outcomes," Working Papers 10197/317, School of Economics, University College Dublin.
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