Back during the presidential debates, Mitt Romney responded to a question about gun violence by invoking the tired old conservative claim that violence is the result of dumb women who forget to get married before they had kids: But let me mention another thing. And that is parents. We need moms and dads, helping to raise kids. Wherever possible the—the benefit of having two parents in the home, and that’s not always possible. A lot of great single moms, single dads. But gosh to tell our kids that before they have babies, they ought to think about getting married to someone, that’s a great idea. It sounded like a non sequitur—as far as I know, no one has shot up a crowd because society forgot to tell them to find a random person to marry prior to childbirth—but Romney was drawing on a long history of claims that single motherhood is the root cause of violence. These claims are based in no small part on the trend lines showing single motherhood and violent crime rising at the same rate. But now here comes Philip Cohen, a University of Maryland sociology professor, with new data. Writing for the Atlantic, Cohen shows that everyone owes single mothers a big apology: For a couple of decades now, single motherhood has continued to rise, but violent crime has been in a freefall since its highs in the 1980s and early ‘90s. Cohen writes: Violent crime has fallen through the floor (or at least back to the rates of the 1970s) relative to the bad old days. And this is true not just for homicide but also for rape and other assaults. At the same time, the decline of marriage has continued apace. Looking at two aggregate trends is never enough to tell a whole story of social change, of course. However, if two trends going together doesn’t prove a causal relationship, the opposite is not quite as true. If two trends do not go together, the theory that one causes the other has a steeper hill to climb. In the case of family breakdown driving crime rates, I don’t think the story will make it anymore. This isn’t a blip. These trendlines have been going in opposite directions for so long that the babies being born when they started to diverge are now out of high school. The people who were so sure that single motherhood was the dominant cause of rising crime rates have had many, many years to revise their opinions and agree to look at other, more complex explanations. And yet, as the Romney example shows, this idea about single mothers causing crime long ago left the world of data to become a faith-based belief. Politically, the claim is a triple-header for conservatives: You can paint urban (and blue) America as a crime-ridden hellhole while distracting people from the issue of gun control and also fear-mongering about single mothers. With hefty political rewards like that, mere data just doesn’t matter.