The Effect of Welfare Payments on the Marriage and Fertility Behavior of Unwed Mothers: Results from a Twins Experiment
利用双胞胎出生作为自然实验，研究福利金对未婚母亲首次结婚时间和再次生育时间的影响，发现较高福利金使白人未婚母亲推迟结婚、黑人未婚母亲加速再次生育，但边际福利金对生育无显著影响。
We study the relationship between welfare benefits and the time to first marriage and time to next birth among initially unwed mothers. We use twin births to generate random within-state variation in benefits, effectively controlling for unobservables that may confound the relationship between welfare payments and behavior. Higher base welfare benefits (1) lead unwed white mothers to forestall their eventual marriage and (2) lead unwed black mothers to hasten their next birth. The magnitudes of these effects are fairly modest. Moreover, we find no evidence that the marginal benefit paid at the birth of an additional childthe focus of the family cap debateaffects fertility.