Does marriage improve well-being for parents and children? It can certainly appear that way. In the contemporary United States, children who grow up with married parents perform better in school, enjoy better physical and emotional health, more often begin and finish college, and enter stable employment at higher rates compared to peers who grow up in other family arrangements (Brown, 2010). Married parents appear to be better off, too: they report being happier, healthier, and more financially secure than parents who are single or in cohabiting unions (Waite, 1995).The relationship between marriage and well-being is of policy interest for several reasons. First, a lot of childrearing in the U.S. happens outside of marriage. Forty percent of U.S. children are born to unpartnered or cohabiting parents (Guzzo, 2021; Osterman et al., 2024, Table 9), and roughly one quarter of children under age 18 live with a single parent, usually their mother (Census Bureau, 2022, Table C3). By age 12, more than half of U.S. children have spent some time outside of a married-parent family household (Brown et al., 2016).Further, in the U.S., children in single-parent households, and particularly those headed by single mothers, are exceptionally likely to be poor, and child poverty is strongly associated with compromised development and achievement (Duncan et al., 1998). Among families with children in 2022, 37.2% of female-headed households and 18.3% of male-headed households were in poverty under the official poverty measure, compared to just 6.9% of married-couple families (Shrider & Creamer, 2023, Table A-2). Among 30 peer countries, the U.S. ranks first for single motherhood's average marginal effect on the probability of being in relative poverty (Brady et al., 2024).And although most Americans say that they would like to marry (Gallup, 2020), married parenthood is largely stratified by race and social class. Sixty percent of Asian adults, 54% of White adults, and 63% of college-educated adults are in married couples today, compared to fewer than half of Black or Hispanic adults and adults with a high school education (31%, 45%, and 45%, respectively; Census Bureau, 2022, Table F2;Julian, 2023). Married adults also have higher earnings at marriage compared to their same-aged unpartnered or cohabiting counterparts (Ludwig & Brüderl, 2018;Oppenheimer, 2003).