Facebook’s user base is shrinking, particularly in the coveted 12- to 34-year-old demographic, according to new survey data compiled by market research firm Edison Research. The survey, which only collected data about users in the US (Facebook’s most lucrative market), found that an estimated 15 million fewer people use Facebook today than they did in 2017, with the biggest drop being among teen users and millennials.

The data is inconclusive on a number of subjects, particularly why people are leaving Facebook, whether some are aging out of a particular demographic and were not counted in the survey, and what type of impact this may have, if any, on the company’s bottom line. (The survey also used randomized phone calls that were then extrapolated to the broader US population; Edison did not call tens of millions of people for the survey.) Going off the company’s most recent earnings report, in which Facebook reported more monthly and daily active users (including in North America) and an all-time high global user base of 2.32 billion, it wold appear business is booming.

But Edison’s survey does signal that the social network’s privacy woes and continued breaches of user trust may at the very least be having some noticeable effect on its most coveted slice of users. “I don’t see how you couldn’t say it’s a meaningful drop. Fifteen million is a lot of people, no matter which way you cut it,” Edison president Larry Rosin told Marketplace in an interview. “It represents about 6 percent of the total US population ages 12 and older. What makes it particularly important is if it is part of a trend. This is the second straight year we’ve seen this number go down.”

Users may be leaving Facebook’s main service to go to Instagram

One interesting element of this trend is that users may not be leaving Facebook entirely, but rather flocking to Instagram instead. The photo-sharing platform, which by its nature collects less personal information from its users, can be a simpler, less toxic alternative to using the main Facebook service, now overrun by ads and plagued by all manner of misinformation, fake news, and other content designed to either generate clicks or influence users for political purposes. It’s also clear that Instagram has now become the hip social network of the younger generation, rivaled only (and barely) by Snapchat. There may be little Facebook can do to reverse that shift.

“There’s conjecture about as Facebook has become more popular among older people, whether that’s affected younger people. Then we have to consider whether some of these other social media platforms, in particular Instagram and Snapchat, are just more appealing to younger people,” Rosin said. “I should also mention that while we’ve seen dramatic reductions in usage among younger people, we’re still seeing some gains among people, for instance, 55 and older.”

Instagram now counts more than 1 billion users and more than 400 million monthly users of its Stories product, a feature originally copied from competitor Snapchat that has now become a vital pillar of how younger users use social media every day and stay engaged with friends online. Facebook has tried to inject some of Instagram’s success back into its main app, primarily by repeatedly attempting to make Stories take off in its Messenger app and main Facebook service. But as it stands today, Facebook’s biggest competitor is another one of its own products, and it seems unlikely the company will stop the shed of users unless it figures out a clever way to unify its services — perhaps through a universal messaging system.

Update 3/6, 4:59PM ET: Clarified that Edison’s survey is providing estimate based on the methodology of the survey, which involved phone calls to numerous US residents that were then extrapolated to the broader US population.