Wage premium of fatherhood and labor supply in Japan

Using data from the Japanese Panel Survey of Consumers (JPSC)1994-2006, we examine the effect of child birth on fathers’ wage rates and labor supply in Japan. We also compare effects of fatherhood among different cohorts by dividing the JPSC sample into two birth year cohorts (born in or before 1960 and born after 1960). We find that birth of child significantly increase hourly wage rates by 2.8 percents and annual work by 65 hours. Comparing with results in the U.S. (Lundberg and Rose 2002), the effect of child birth on labor supply is large but the effect on wage rates are relatively small in Japan. We also find that child birth have different impact on labor market outcome between the early and the later cohorts. In the early cohort, birth of child significantly increases wage rates but has no significant effect on labor supply. On the contrary, birth of child does not increases wage rates but significantly increases labor supply in the later cohort. Finally, we examine how gender difference of children matters. Although the impact of gender difference is not so large, the effect of birth of sons is larger than the effect of birth of daughters.child birth; labor supply; wage premium

Magnetization Degree of Gamma-Ray Burst Fireballs: Numerical Study

The relative strength between forward and reverse shock emission in early gamma-ray burst afterglow reflects that of magnetic energy densities in the two shock regions. We numerically show that with the current standard treatment, the fireball magnetization is underestimated by up to two orders of magnitude. This discrepancy is especially large in the sub-relativistic reverse shock regime (i.e. the thin shell and intermediate regime) where most optical flashes were detected. We provide new analytic estimates of the reverse shock emission based on a better shock approximation, which well describe numerical results in the intermediate regime. We show that the reverse shock temperature at the onset of afterglow is constant, $(\bar{\Gamma}_d-1)\sim 8\times10^{-2}$, when the dimensionless parameter $\xi_{0}$ is more than several. Our approach is applied to case studies of GRB 990123 and 090102, and we find that magnetic fields in the fireballs are even stronger than previously believed.Comment: 22 pages, 5 figures, accepted to Ap