[영문]Much of the sharp rise in the share of nonmarital births in the United States has been attributed to changes in the fertility choices of unmarried and married women?in response, it is often argued, to public policy. In contrast, we develop and test a model that attributes the rise to changes in marriage behavior, with no necessary changes in fertility. A variety of empirical tests strongly support this conclusion and invites focused attention to issues related to marriage behavior as well as to the interactions between marriage and fertility.