I don’t know why parents didn’t trust the network responsible for “Jersey Shore” and “Catfish” to treat a subject like teen pregnancy sensitively rather than as campy reality-celebrity freak-show fun.

Strictly speaking, what the study shows is that the teen birthrate fell more steeply in areas where more teens were watching MTV. The idea that teens are being scared straight by the show “16 and Pregnant” specifically is an assumption, but a logical one. The sense I get from the NYT piece is that this is going to become a proxy for approaches to sex ed — for lefties, evidence that frankly confronting a taboo subject leads to more responsible sexual behavior, and for righties, evidence that deglamorizing sex by emphasizing its potential hardships is important in teaching kids.

A new economic study of Nielsen television ratings and birth records suggests that the show she appeared in, “16 and Pregnant,” and its spinoffs may have prevented more than 20,000 births to teenage mothers in 2010.

The paper, to be released Monday by the National Bureau of Economic Research, makes the case that the controversial but popular programs reduced the teenage birthrate by nearly 6 percent, contributing to a long-term decline that accelerated during the recession…

Ms. Kearney and Mr. Levine examined birth records and Nielsen television ratings, finding that the rate of teenage pregnancy declined faster in areas where teenagers were watching more MTV programming — not only the “16 and Pregnant” series — than in areas where they did not. The study focuses on the period after “16 and Pregnant” was introduced in 2009 and accounts for the fact that teenagers who tuned in to the show might have been at higher risk of having a child to begin with.

“The assumption we’re making is that there’s no reason to think that places where more people are watching more MTV in June 2009, would start seeing an excess rate of decline in the teen birthrate, but for the change in what they were watching,” Mr. Levine said.

The impact was greatest among black teens, according to the Times; whether that’s because the teen birth rate among that group had more room to fall or because of some other cultural element of the show is hard to say. The whole point of 16&P, it seems, is to de-normalize teen pregnancy as something so extraordinary, fraught, and disruptive as to merit its own TV treatment. The less accustomed you are to seeing it that way, I assume, the more of an impact it’ll have. One open question, though: What, specifically, is responsible for the reduction in births? If this really is a pop-cult sex ad class, what’s the core lesson teens are taking away from it — abstinence, contraception, or abortion? The study tracked social-media mentions of 16&P after each episode aired and found that the words “contraception” and “abortion” were both used more frequently afterward. Hmmmm.

Hollywood and the TV industry love to emphasize how influential they are when the result of that influence is good but ferociously resist accusations of influence when the result is bad. Here’s proof, seemingly, and to no one’s surprise, that mass media’s approach to a social problem can move the needle. And if it can move this way, why not the other way? Makes me wonder: Will 16&P’s success start a trend of scared-straight programming aimed at teens? MTV’s never going to do a show about, say, the aftermath of abortion, but some other conservative-leaning outfit might. Now all we have to do is figure out a way to get that in front of a wide audience.