Though estimates vary, as many as 2 million to 3.7 million U.S. children under age 18 may have a lesbian, gay, bisexual, or transgender parent, and about 200,000 are being raised by same-sex couples. Much of the past decade's legal and political debate over allowing same-sex couples to marry has centered on these couples' suitability as parents, and social scientists have been asked to weigh in. After carefully reviewing the evidence presented by scholars on both sides of the issue, Gary Gates concludes that same-sex couples are as good at parenting as their different-sex counterparts. Any differences in the wellbeing of children raised in same-sex and different-sex families can be explained not by their parents' gender composition but by the fact that children being by raised by same-sex couples have, on average, experienced more family instability, because most children being raised by same-sex couples were born to different-sex parents, one of whom is now in the same-sex relationship. That pattern is changing, however. Despite growing support for same-sex parenting, proportionally fewer same-sex couples report raising children today than in 2000. Why? Reduced social stigma means that more LGBT people are coming out earlier in life. They're less likely than their LGBT counterparts from the past to have different-sex relationships and the children such relationships produce. At the same time, more same-sex couples are adopting children or using reproductive technologies like artificial insemination and surrogacy. Compared to a decade ago, same-sex couples today may be less likely to have children, but those who do are more likely to have children who were born with same-sex parents who are in stable relationships. In the past, most same-sex couples raising children were in a cohabiting relationship. With same-sex couples' right to marry now secured throughout the country, the situation is changing rapidly. As more and more same-sex couples marry, Gates writes, we have the opportunity to consider new research questions that can contribute to our understanding of how marriage and parental relationships affect child wellbeing.