In recent years, the Internet has nearly buckled under the weight of think pieces dedicated to explaining the rise of the unmarried mother. And for good reason. The birth rate to unmarried mothers has, with a few pauses, steadily climbed since the 1940s.

But as a new report from the Centers for Disease Control and Prevention shows, the most recent upward trend, begun in 2002, seems to have reversed, in the steepest decline ever recorded, dropping 14 percent from its 2007 peak, to 44.8 per 1,000 women of childbearing age (15-44). The number of births to unwed mothers also dropped 7 percent, to approximately 1.6 million, from 2012 to 2013. Mostly women under 30 years old drove the declines. Hispanic and black women saw the biggest drops.

So what’s happening?

The most obvious explanation for the lower rate in, as family-values conservatives sometimes phrase it, “illegitimate” children, has to do with an overall decrease in the birth rate. The fertility rate fell to a record low in 2013, so it makes sense that if all women are having fewer babies, then the rate to unwed mothers would fall, too. But the birth rates for married women haven’t fallen as quickly as those of their unwed counterparts, and have actually increased slightly.

Much of the decrease, though not all, can be attributed by the continuing downward trend of teen pregnancy, a finding hailed in recent years and explained by factors like better contraception and changing attitudes surrounding young moms. (One National Bureau of Economic Research study attributed a third of the decline to MTV’s show, Teen Mom.) The most recently available data show the birth rate for teenagers ages 15-19 dropped to its lowest rate ever in 2012—29.4 per 1,000—a 6 percent decrease from the previous year.

But despite public perception, teen moms and unmarried moms aren’t the same thing; teen births represent only about 15 percent of nonmarital births. The largest number of births outside of marriage come from mothers in their 20s, but even that may change soon, as the teen birth rate decline seems to be spreading to the slightly older unmarried women. Women over 30 are now choosing to have children outside of marriage. In 2012 the birth rate for unmarried women aged 30-34 substantially surpassed that of unmarried 18- and 19-year-olds for the first time.

“We’re not sure exactly why this is happening to women in their 20s,” said Andrew Cherlin, a sociologist at Johns Hopkins University whose recent study showed that less educated millennial moms are more likely to have kids outside of marriage. “I doubt it’s because of a decline in sexual activity. It probably suggests better contraception.”

It’s interesting to note in the report that the oft-cited statistic of four in 10 children being born to unwed mothers won’t change because of the rate drop. The percentage of births occurring outside of marriage has remained stable after years of steady increase.

What has changed, substantially and perhaps for the best, is just what a nonmarital birth looks like. An unmarried parent isn’t necessarily a single parent. These days, a child born to an unwed mother is much more likely to be part of a cohabiting family. Almost three in five births to unwed women are to women who are cohabitating with a partner. In 2002 and the years 2006-10, the percentage of children born to cohabiting parents rose from 41 percent to 58 percent.

“It may be seen as ‘better’ than living alone, but these relationships are quite unstable, and we know that upwards of 40 percent of these cohabiting relationships are formed after the woman gets pregnant,” Cherlin said. “Some people talk about shotgun cohabitation, only there’s nobody holding the shotgun anymore.”

While acknowledging the relative instability of cohabitation vs. marriage (“They’re more likely to end and as a result, children are more likely to experience turbulence in their family situations”), Jennifer Manlove, senior researcher at Child Trends, a nonprofit that studies the health and well-being of children, told The Daily Beast, “This is positive news.”

“Children growing up in families with cohabiting parents are more likely to have more resources and more parental involvement,” she said And a recent study shows cohabiting fathers are likely to be as involved as married ones.

Though it’s not perfect, and it surely won’t appease the family values warriors, shotgun shacking up is probably here to stay.

“Four in 10 births are outside of marriage.” Manlove said. “That’s not going to reverse in a big way. It hasn’t gone down even as the nonmarital birth rates have. I think this is the family formation of the future and so there needs to be approaches to improving well-being in these types of families.”