TY  - JOUR
AU  - Black,Sandra E.
AU  - Devereux,Paul J.
AU  - Salvanes,Kjell G.
TI  - Small Family, Smart Family? Family Size and the IQ Scores of Young Men
JF  - National Bureau of Economic Research Working Paper Series
VL  - No. 13336
PY  - 2007
Y2  - August 2007
UR  - http://www.nber.org/papers/w13336
L1  - http://www.nber.org/papers/w13336.pdf
N1  - Author contact info:
Sandra Black
Department of Economics
University of Texas
Austin, TX  78712
Tel: 512-475-8519
E-Mail: sblack@austin.utexas.edu

Paul J. Devereux
School of Economics
and Geary Institute
University College Dublin
Belfield, Dublin 4
Ireland
E-Mail: devereux@ucd.ie

Kjell Salvanes
Department of Economics
Norwegian School of Economics
Hellev. 30, N-5035 Bergen
Norway
E-Mail: kjell.salvanes@nhh.no
AB  - 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.
ER  -