But research doesn’t have to use random samples to be scientific. The scientific method demands systematic analysis based on empirical observation. While large random samples are the gold standard, that doesn’t mean that all other research is unscientific. It just lessens—somewhat—its predictive value. And bear in mind that even the largest research studies on public policy issues only offer predictions, not guarantees, about future outcomes. The difference here is one of degree.
What does the social science actually tell us? Statistics on marriage rates show consistently that they have not dropped in states and countries that allow gay marriage, as examined in Slate. But since gay marriage is so new, so are these results, and no one ever promised civilization would end in a day.
The bulk of the controversy surrounds research on gay parenting. At least 45 scholarly studies have compared children of gay and straight parents and found no disadvantages to the former. It’s true that many have small, nonrandom sample sizes—often about 30-50 families. But when you aggregate 45 consecutive studies—even small ones—that all reach the same conclusion, what you end up with is an almost unheard-of scholarly consensus. “Rarely is there as much consensus in any area of social science as in the case of gay parenting,” said Judith Stacey, the New York University sociologist who is one of the deans of gay parenting scholarship.
In any event, not all the studies are small or nonrandom. A 2010 Stanford study used census data, instead of a convenience sampling or self-reporting, to examine 3,500 children of same-sex couples. It compared their school progress to more than 600,000 kids of straight parents and found no differences. Other studies are “longitudinal,” increasing statistical reliability by tracking developments over many years. The longest-running and largest such study, the U.S. National Longitudinal Lesbian Family Study, followed 78 lesbian-headed households for more than 25 years. Led by Nanette Gartrell, a UCLA-based psychiatrist and researcher, the study found no disadvantages (and a few advantages) to children with lesbian moms.
Is there any research showing disadvantages for kids with gay parents? Try as they might, conservative scholars, often funded by anti-gay think tanks, have failed to produce a single study. In the most embarrassing recent effort, University of Texas professor Mark Regnerus was formally reprimanded for publishing a study (which he wrote about for Slate) that he claimed had a massive sampling pool; in reality the number of children of same-sex couples he surveyed was a whopping two. (Last week it was reported that conservative funders bankrolled the study and urged Regnerus to rush it to maximize its influence on the Supreme Court.) Whatever you may say about the limits of the gay parenting studies—and all research has limits—the pro-gay research is currently winning, 45-0.
Absent actual evidence, the religious right has routinely used studies of single-parent and divorced households to allege that any family lacking a father—that is, even if it has two loving moms—is bad for kids. They cite research showing that two parents are better than one, and since all that research has focused on opposite-sex parents, they conflate number with gender and rally around the talking point that kids need “a mother and a father.” Appallingly, George Will has now stooped to this level, citing the allegation of conservative scholars that “research concluded that growing up without fathers had significant negative effects on boys,” even though that research never included households with two gay parents—and this after complaining about “inappropriate invocations of spurious social science” by liberals.
None of this should matter. Even if gay parenting did disadvantage kids, it wouldn’t follow that gay marriage should be banned since gay people—like single and divorced people—will have kids no matter what. How could banning gay marriage help those—or any—kids? And if we based straight marriage rights on predicting durability, half the country wouldn’t be allowed to wed.
But the research does matter, because conservatives have made it matter, and it may very well influence the Supreme Court. It’s true we don’t know everything about gay marriage and parenting, but what we do know is important to get right.