Major changes in life course patterns regarding marriage, including later marriage, and increases in divorce and nonmarital childbearing, have been collectively referred to as a “retreat from marriage.” These changes have been observed in all industrialized countries since the second half of the 20th century and are expected to have major demographic, social, economic, and political implications. Of particular importance are the acceleration of population decline and aging through fertility decline and the exacerbation of socioeconomic inequality through decreases in the well-being of specific groups of people. In this project, I focus on the latter aspect, attempting to clarify how behaviors associated with the retreat from marriage influence the well-being of mothers and children. In Japan, a series of changes in partnership formation and dissolution has led to the diversification of childbearing and parenting patterns. Childbearing via bridal pregnancy (i.e., “shotgun weddings”), out of wedlock childbearing, and single parent families have all increased in recent years. Although we know that single-mother families face severe economic disadvantage, existing research has not sufficiently clarified which aspects of the retreat from marriage are most relevant in accelerating or moderating the negative consequences of single parenthood. In this project, I will approach these questions using two large national sample surveys, and suggest how these situations may differ from those documented in existing research on the U.S. First I intend to use a large scale, longitudinal survey of infants to examine how multiple measures of mothers’ well-being (e.g., mothers’ socioeconomic status, worries about childcare, support from mothers’ parents, presence of a partner) differ for those who experienced nonmarital family formation (i.e., out of wedlock childbearing, premarital pregnancy, or divorce) and those who followed a “standard” pattern of family formation (i.e., first child conceived within a stable marital relationship). Positing that discrimination or normative disapproval of nonmarital family formation may accelerate the negative outcomes among mothers and children in such families, I will also conduct Japan-U.S. comparisons regarding attitudes toward nonmarital childbearing and divorce. Using cross-sectional surveys, I will examine how acceptance of these behaviors is associated with women’s individual characteristics, including socioeconomic status. Comparison between Japan and the US, which have similar economic systems but very different cultural circumstances regarding gender and intergenerational relations, will be a potentially valuable source of general theoretical insight into the importance of social and cultural context for understanding relationships between the retreat from marriage and the well-being of mothers and children. It may also provide important insights into the future of East Asian countries facing similar trends in the retreat from marriage. The Center for Demography and Ecology at the University of Wisconsin has played a pioneering role in the field of quantitative family studies using the kind of longitudinal survey data that we have only recently begun to collect in Japan. With CDE as my research base, I will be able to deepen my understanding of the newest research on nonmarital family formation in the U.S through formal and informal interaction with family scholars in the U.S.