Small Family, Smart Family? Family Size and the IQ Scores of Young Men

38 Pages Posted: 24 Aug 2007 Last revised: 4 Mar 2010

See all articles by Sandra E. Black

Sandra E. Black

University of Texas at Austin - Center for Law, Business, and Economics; National Bureau of Economic Research (NBER); IZA Institute of Labor Economics; Norwegian School of Economics (NHH) - Department of Economics

Paul J. Devereux

University College Dublin - Department of Economics; IZA Institute of Labor Economics

Kjell G. Salvanes

Norwegian School of Economics (NHH) - Department of Economics; IZA Institute of Labor Economics

Multiple version iconThere are 3 versions of this paper

Date Written: August 2007

Abstract

How do families influence the ability of children? Cognitive skills have been shown to be a strong predictor of educational attainment and future labor market success; as a result, understanding the determinants of cognitive skills can lead to a better understanding of children's long run outcomes. This paper uses a large dataset on the male population of Norway and focuses on one family characteristic: the effect of family size on IQ. Because of the endogeneity of family size, we instrument for family size using twin births and sex composition. IV estimates using sex composition as an instrument show no negative effect of family size; however, IV estimates using twins imply that family size has a negative effect on IQ. Our results suggest that effect of family size depends on the type of family size intervention. We conclude that there are no important negative effects of expected increases in family size on IQ but that unexpected shocks to family size resulting from twin births have negative effects on the IQ of existing children.

Suggested Citation

Black, Sandra E. and Devereux, Paul J. and Salvanes, Kjell G., Small Family, Smart Family? Family Size and the IQ Scores of Young Men (August 2007). NBER Working Paper No. w13336. Available at SSRN: https://ssrn.com/abstract=1008828

Sandra E. Black (Contact Author)

University of Texas at Austin - Center for Law, Business, and Economics ( email )

Austin, TX
United States

National Bureau of Economic Research (NBER) ( email )

1050 Massachusetts Avenue
Cambridge, MA 02138
United States

IZA Institute of Labor Economics

P.O. Box 7240
Bonn, D-53072
Germany

Norwegian School of Economics (NHH) - Department of Economics

Helleveien 30
N-5035 Bergen
Norway

Paul J. Devereux

University College Dublin - Department of Economics ( email )

Dublin 4, 4
Ireland

IZA Institute of Labor Economics

P.O. Box 7240
Bonn, D-53072
Germany

Kjell G. Salvanes

Norwegian School of Economics (NHH) - Department of Economics ( email )

Helleveien 30
N-5035 Bergen
Norway
+47 5 595 9315 (Phone)
+47 5 595 9543 (Fax)

IZA Institute of Labor Economics

P.O. Box 7240
Bonn, D-53072
Germany

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