The Legacy of China's One-Child Policy on Human Capital: How Being Raised by an Only Child Affects Cognitive and Noncognitive Skill Development

China's One-Child Policy (OCP) restricted most couples to a single birth, leading to a rapid increase in the prevalence of only children. Using longitudinal data and a regression discontinuity design around the policy's start, we estimate the effects on grandchildren's human capital. We find that children with only-child mothers perform significantly better in cognitive skills (0.71 SD) and noncognitive skills (0.50 SD) than comparable peers. The effects are larger for boys, consistent with son preference, and for those with less-educated grandparents, for whom quantity-quality trade-offs are more applicable. Additionally, we find that only-child parents have higher educational attainment and provide more favorable home environments, which may explain their children's advantages in human capital outcomes. These findings suggest that, in the presence of quantity-quality trade-offs, fertility restrictions can improve human capital across multiple generations.