Remember the old Oldsmobile ad? “It’s not your father’s Oldsmobile.” The sales pitch was meant to counteract the perception of an Olds as an old-person’s car, inviting younger drivers to check out its new, hip, youthful-looking style and performance.

Maybe Mark Zuckerberg should hunt down the agency that created that ad campaign and sign them up, because the social media platform that was created originally for college-age users is tanking among that very age group these days.

According to eMarketer’s latest forecast, Facebook is rapidly becoming the Oldsmobile of social media platforms, a place increasingly seen as one used by an older generation, who are crowding out their grandkids.

“This year, for the first time, less than half of U.S. Internet users ages 12 to 17 will use Facebook via any device at least once per month,” the New York-based research firm announced. eMarketer has warned about the fading appeal of Facebook for teens several times in the past six months. This is a huge problem for Facebook, which needs a young demographic to open Facebook, to continue advertising to them into adulthood.

“Facebook is still adding monthly users overall, but older age groups are mainly responsible for this,” eMarketer said. “The number of total Facebook users in the U.S. will reach 169.5 million this year, up just under 1 percent from 2017. Meanwhile, Facebook’s proportion of social network users accessing the platform will continue to decline over the forecast period.”

Facebook is forecasted to lose 2 million additional users under the age of 25 this year.

So what’s happening to all these younger users? In a word, Snapchat. And, to a slightly lesser degree, Instagram. The same eMarketer forecast predicted that Instagram will add 1.6 million users while Snapchat will pick up 1.9 million users within that age bracket.

According to CNBC, Snapchat recently updated its app with an easier-to-use redesign, and the effort has apparently paid off. “The overhaul kept the social element of the app separate from media, with one page devoted to interacting with friends’ Snapchat stories and messages, while another runs a feed of video content from media outlets,” CNBC said.

Julie Smith, a social scientist in Denver who works with teens, told USA Today:

“They now call Facebook “the old-people network.””

“Teens want that instant gratification. That’s why Snapchat and Instagram work well for them. Their minds move quickly,” she said. “Facebook feels like an investment of their time, and they don’t want to invest their time in it.”

“Snapchat could eventually experience more growth in older age groups, since it’s redesigning its platform to be easier to use,” Debra Aho Williamson, principal analyst at eMarketer, 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.”

So what does this mean for your business? As always, you must know your target demographic. If your products or service caters to teens and millennials, you’ll want to move much of your marketing to Instagram.

But this also doesn’t mean you can drop Facebook entirely. “Less than half” of users ages 12 to 17 could be turned around and read “nearly half” of that age group still using the platform, for now. But you need to be aware of the fact that Facebook is in trouble with that demographic and, unless it does something drastic to turn itself around, will likely continue losing those users.