For the first time in a while, less than half of American internet users between ages 12 and 17 will be using Facebook this year, according to research firm eMarketer.

What’s more, usage among 18-24 year-olds is predicted to fall, as well, by 5.8%. The firm also says that growth will keep falling for both groups for the next two years. Facebook will still continue to add users overall, but at a slower pace, predicted to be about 1% in 2018, and the growth will be chiefly among its older demographics.

EMarketer’s estimates are based on an analysis of survey and traffic data from other research firms and regulatory agencies, Facebook’s own disclosures, historical trends, and demographic and socioeconomic factors, the firm told Quartz. A user is defined as someone who logs onto a platform at least once per month.

During its latest earnings call, Facebook reported that the number of daily active users in the US and Canada fell for the first time ever, by about 700,000. The company says it is not worried about the drop, since the US market is already so saturated, and because it attributes the decrease to its own, purposeful moves to revamp the News Feed algorithm.

EMarketer estimates that the company will lose two million users under 25 this year. This should be worrying for the Facebook on two levels: Having the future in mind, you don’t want your users to be aging, and the US market is by far the company’s most profitable.

And then there’s another issue. While the company could be banking on Instagram as its platform for the younger demographic, the research firm says that the users who are leaving Facebook are not necessarily migrating to Instagram. It says that Facebook’s photo-sharing platform will add about 1.6 million users under 25, while Snapchat, whose results beat expectations for the last quarter of 2017, will add 1.9 million users in that age group.

“Snapchat could eventually experience more growth in older age groups, since it’s redesigning its platform to be easier to use,” Debra Aho Williamson, a principal analyst for the firm said in a statement. “The question will be whether younger users will still find Snapchat cool if more of their parents and grandparents are on it. That’s the predicament Facebook is in.”