Teens are having less sex than they used to, new data from the Centers for Disease Control and Prevention show.

The percentage of teens who reported having had sex at least once has dropped significantly since the late 1980s — down 13 percentage points for boys and 6 percentage points for girls.

The percentage of teens who used contraception the first time they had sex has not changed over the same time period, the CDC says. Seventy-nine percent of teenage girls and 84 percent of teenage boys reported using some method of protection.

What has changed a bit is the type of protection that teenagers use. That's what you see in this chart, which surveys adolescents on whether they've used any of the following types of protection:

The most significant difference appears to be in use of emergency contraception, which has nearly tripled in the past decade. This likely reflects changes to federal rules: Plan B moved to over-the-counter for women over 17 in 2009, and then became available for women over 15 in 2013. Easier access to the contraceptive appears to be translating to more usage.

The decline in teenagers having sex could be one factor that helps explain why the teen birth rate has fallen rapidly since the 1990s, hitting a new all-time low of 29.4 births per 1,000 teenagers in 2013.

Further reading: You can read more about the falling teen birth rate in this longer feature I published this past January, which explores all the different reasons teens are having fewer babies than ever before. And for more on how teenagers' behavior is changing — mostly for the better — check out this other piece from last year.

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