Teens have abandoned Facebook in large numbers, new research reveals. About half (51 percent) of U.S. teens ages 13 to 17 say they use Facebook, down from 71 percent in 2015, according to a recent Pew Research Center survey. More teens say they use YouTube (85 percent), Instagram (72 percent) and Snapchat (69 percent). That’s a significant shift in teen social media habits in just the last three years. In the beginning, it was teens who popularized Facebook.

In the center’s 2014-2015 survey, 71 percent of teens said they were Facebook users. About half (52 percent) said they used Instagram and 41 percent Snapchat. YouTube and Reddit were not included in that survey.

Instagram’s growing popularity may please Facebook, which owns that platform, but more teens now visit competing platforms more frequently. About a third say they visit Snapchat (35 percent) or YouTube (32 percent) most often, while 15 percent say they visit Instagram the most. Only 10 percent of teens say they visit Facebook most frequently.

The Impoverishment of Facebook Demographics

The survey also shows that lower-income teens are more likely to gravitate toward Facebook than those from higher-income households. Seven-in-ten teens living in households earning less than $30,000 a year say they use Facebook, compared with 36 percent whose annual family income is $75,000 or more. Lower-income teens are also more likely than peers in higher-income households to visit Facebook most often (22 percent vs. 4 percent).

Previous Pew research shows Facebook tends to attract lower-income, less-educated users at higher rates than other networks. About two-thirds of US adults earning less than $30,000 use Facebook, compared to 20 percent for Twitter and 13 percent for LinkedIn.

The impoverishment of Facebook’s demographics may pose a threat to Facebook’s business model, says Frederic Filloux, editor of the Monday Note. But Facebook still has room to grow, at least over the next few years, given the large number of business users who don’t advertise. Its ownership of Instagram and Messenger provides additional opportunities for advertising revenue.

Why Teens Don’t Like Facebook

Many observers believe teens no longer consider Facebook cool because their parents and other older frequent the network.

Teens may dislike what Facebook’s algorithm shows them. The average person views just a fraction of the thousands of posts in their newsfeed. Its algorithm prioritizes content based on the user’s engagement history but must balance users’ preferences with its own commercial interests: the ability to bring in advertising income through clicks.

“It’s unclear (and a well-kept secret) how Facebook deals with this contradiction,” Filloux says. “However, the company is known to be literally obsessed with business-related KPIs, perhaps at the expense of the relevance of the newsfeed.”

People may want to control what they view, he adds. Other networks provide users more control. YouTube users simply pick what they want to view.

Facebook remains the most popular network among older generations. About two-thirds of U.S. adults visit Facebook, and roughly three-quarters of those access it daily. However, if the teens retain their social media preferences as they age, which is likely, Facebook faces a worrisome long-term danger.

Bottom Line: Facebook’s loss of teen-aged and higher-income users portends substantial long-term challenges for the leading social media network. The trends are also important for PR and marketing teams targeting certain demographic groups. If current trends continue, brands offering higher-cost or luxury products may turn to other networks.