This report uses data from the Fragile Families and Child Well-Being Study (a nationwide survey that collects data on married and non-married parents at the time of the child's birth) to determine how much marriage could reduce poverty among couples who are not married at the time of birth. To determine the impact of marriage on children's and mothers' poverty, the study estimated what the mothers' poverty rate would be if they remained single, calculated what the poverty rate would be if the mothers and fathers married, then noted differences between poverty rates. The effect of marriage on poverty was calculated according to three scenarios regarding the mother's employment after childbirth (zero annual employment, part-time employment, and full-time employment). Data analysis indicates that marriage would dramatically reduce poverty among non-married mothers who are romantically involved with the fathers at the time of the child's birth. Specifically, if these mothers do not marry but remain single, about 55 percent will be poor. By contrast, if all mothers married their child's father, the poverty rate would fall to less than 17 percent. Thus, on average, marriage would reduce the odds that a mother and a child will live in poverty by more than 70 percent. A technical appendix describes how researchers used the Fragile Families survey and database to simulate the effects of marriage on child poverty. (Contains 15 footnotes.) (SM)