NBER Working Papers · 2026 · Dora L. Costa、Matthew E. Kahn
中文摘要
我们展示了生育延迟如何在代际间累积，从而提高首次成为祖母的年龄。按照1960年的初育时间表，首次成为祖母的中位年龄为44岁；按照2024年的时间表，这一年龄为57岁，使祖母能够与孙辈共度的健康年限从28年缩短至15年。寿命延长并不能弥补祖母身体足够健康、能够提供金钱支持和照护的年限损失。延迟在受过大学教育的人群中最为明显；在白人大学毕业生中，生育控制手段的可及性解释了截至55岁已成为祖母的比例降幅的一半以上。当女儿为最大化自身收益而选择初育时间时，她的选择给母亲造成的损失未被纳入她自身的收益计算。我们将此称为“不肖成年子女问题”（Rotten Adult Kid Problem）。生育延迟既提高了祖母照护的价格，也增加了每名孙辈对应的财富。
Abstract
We show how fertility delays compound across generations to raise age at first grandmotherhood. Under the 1960 first-birth schedule median grandmotherhood came at 44. Under the 2024 schedule it is 57, cutting the healthy years with grandchildren from 28 to 15. Longer life does not make up the loss of years when the grandmother is healthy enough to supply money and care. Delay is most pronounced among the college-educated, with reproductive-control access accounting for over half the fall in grandmotherhood by age 55 among White college graduates. When a daughter times her first birth to maximize her own payoff, the loss her choice imposes on her mother is external to her calculation. We call this the Rotten Adult Kid Problem. Delay raises both the price of a grandmother's care and wealth per grandchild.