What do the half-century decline in U.S. marriage and the attendant rise in single parenthood mean for the economic well-being of children, especially children living in single-parent families? Adam Thomas and Isabel Sawhill show how differing living arrangements can be expected to affect families’ economic well-being. Married-parent and cohabiting households, for example, can benefit from economies of scale and from having two adult earners. The availability of child support for single-parent families and the marriage penalties in the tax and transfer system reduce, but rarely completely offset the economic benefits of marriage. (Author abstract)