Birth order and intergenerational income mobility in Japan: Is the first-born child different?

This study examines how birth order affects intergenerational income mobility (IGM) in Japan, focusing on the difference in IGM between firstborn and later-born children. The elasticities of sons’ income with respect to fathers’ income are separately estimated for sons who are firstborn and sons who are later born by family size using a two-sample, two-stage least squares approach. For sons born in 1926–1981, this study finds that in families with four or more children, intergenerational income elasticity (IGE) for firstborn sons is substantially and significantly higher than that for later-born sons. However, no significant birth order effects are found in households with two or three children.