The share of teen girls who reported they’ve had sex at least once dropped from 51 percent in 1988 to 44 percent in 2013, they found. Abstinence was more pronounced among the guys: 60 percent of teen boys in 1988 said they’d had sex, compared to 47 percent in 2013.
That is from Paquette and Cai, the underlying CDC study is here. One major hypothesis is that teen sex has declined because smart phone usage is up. Teens are both better informed about the risks of sex and…they have something else to do.