There is an extensive theoretical literature that postulates a trade-off between child quantity and quality within a family. However, there is little causal evidence that speaks to this theory. Using a rich data set on the entire population of Norway over an extended period of time, we examine the effects of family size and birth order on the educational attainment of children. We find a negative correlation between family size and children's education, but when we include indicators for birth order or use twin births as an instrument, family size effects become negligible. In addition, higher birth order has a significant and large negative effect on children's education. We also study adult earnings, employment, and teenage childbearing and find strong evidence for birth order effects with these outcomes, particularly among women. These findings suggest the need to revisit economic models of fertility and child "production," focusing not only on differences across families but differences within families as well.

Lower birth weight babies have worse outcomes, both short-run in terms of one-year mortality rates and longer run in terms of educational attainment and earnings. However, recent research has called into question whether birth weight itself is important or whether it simply reflects other hard-to-measure characteristics. By applying within twin techniques using an unusually rich dataset from Norway, we examine the effects of birth weight on both short-run and long-run outcomes for the same cohorts. We find that birth weight does matter; despite short-run twin fixed effects estimates that are much smaller than OLS estimates, the effects on longer-run outcomes such as adult height, IQ, earnings, and education are significant and similar in magnitude to OLS estimates.

Economists and social scientists have long been interested in intergenerational mobility, and documenting the persistence between parents and children's outcomes has been an active area of research. However, since Gary Solon's 1999 Chapter in the Handbook of Labor Economics, the literature has taken an interesting turn. In addition to focusing on obtaining precise estimates of correlations and elasticities, the literature has placed increased emphasis on the causal mechanisms that underlie this relationship. This chapter describes the developments in the intergenerational transmission literature since the 1999 Handbook Chapter. While there have been some important contributions in terms of measurement of elasticities and correlations, we focus primarily on advances in our understanding of the forces driving the relationship and less on the precision of the correlations themselves.

Parents with higher education levels have children with higher education levels. However, is this because parental education actually changes the outcomes of children, suggesting an important spillover of education policies, or is it merely that more able individuals who have higher education also have more able children? This paper proposes to answer this question by using a unique dataset from Norway. Using the reform of the education system that was implemented in different municipalities at different times in the 1960s as an instrument for parental education, we find little evidence of a causal relationship between parents' education and children's education, despite significant OLS relationships. We find 2SLS estimates that are consistently lower than the OLS estimates with the only statistically significant effect being a positive relationship between mother's education and son's education. These findings suggest that the high correlations between parents'and children's education are due primarily to family characteristics and inherited ability and not education spillovers.

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