There are three million fewer teens using Facebook in the U.S. than there were in 2011, according to iStrategy Labs, a digital agency that has tracked "addressable" Facebook users in the Facebook ad system.
iSL tracks users through Facebook's advertising interface, in which advertisers can slice and dice segments of users and buy whatever audience demographics they want. In 2011, there were 13.1 million teens available for advertisers to target. This year, there are only 9.8 million users aged 13-17 available, iSL says.
That's a decline of -25.3% .
Here are the numbers, per iSL:
iSL
Users aged 18-14 also slipped, from 45.4 million to 42 million iSL's data show.
The stats dovetail with Facebook's own admission on its Q3 2013 earnings call that it had seen a slight dropoff in teen use of the site. Since then, there has been a slew of headlines about teens who say they are bored of Facebook because their parents are on it, and they're moving to other apps such as Snapchat and Instagram (which Facebook also owns).
When Facebook first indicated its teen users were in a slight decline, the stock fell by 15% on the day.
Here's iSL's previous take on teen users, from back in 2011:
iSL