Fertility and maternal labor supply in Japan: Conflicting policy goals?

Using panel data on Japanese mothers, this paper estimates the impact of fertility on maternal labor supply using twins as an instrument for the total number of children. We find that having twins actually has a longer term positive impact on maternal labor force participation in Japan. To understand this result, we present evidence that the effects of age and cost of children can generate this finding, are particularly salient in Japan and differ in important ways between twins and non-twin families of the same size. Implications for fertility and labor supply policy in Japan are discussed.     

Estimates of the return to schooling in Sweden from a large sample of twins

A large sample of twins was used to examine whether conventional estimates of the return to schooling in Sweden are biased because ability is omitted from the earnings–schooling relationship. Ignoring measurement error, the results indicate that omitting ability from the earnings–schooling relationship leads to estimates that are positively biased. However, reasonable estimates of the measurement-error-adjusted returns are both above and below the unadjusted estimates, showing that the results depend crucially on a parameter not known at this time. However, an estimate of the reliability ratio was obtained using two measures on educational attainment. With this estimate of the reliability ratio, the measurement-error-adjusted estimate of the return to schooling in the sample of identical twins indicates that there is at most a slight ability bias in the conventional estimates of the return to schooling. The fundamental assumption of this kind of study is that within-pair differences in educational attainment are randomly determined. This assumption was also tested, but no strong evidence to reject it was found.