Facebook may have been breathing a sigh of relief recently when data showed the Cambridge Analytica scandal and the resulting #DeleteFacebook movement hadn't really taken off -- in fact, usage was up. But this week, there is renewed reason for concern. Lots of folks may still be using Facebook, but it appears the site's popularity is plummeting with one key demographic -- teens.

Facebook has fallen out of favor with the group that generally pioneers online trends, according to new data from Pew. Here are a few key numbers from the study:

  • 51 percent of 13 to 17-year-old Americans surveyed said they use Facebook, down from 71 percent just three years ago.

  • Instagram (72 percent) and Snapchat (69 percent) are now vastly more popular.

  • YouTube was the most popular service of all, with 85 percent of teens saying they use the site (Pew had not previously asked about the platform).

Pew also notes that, while these numbers are largely consistent, there is one noticeable demographic difference in usage. Richer teens use Facebook less than poorer ones. "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," the research found. Other platforms didn't have a similar split based based on income.

While various sites have risen or fallen in the affections of teens, one trend continues with rock solid steadiness. Kids spend a lot of time online, and it's only increasing. This time around nearly half of teens (45 percent) told Pew that they were online 'nearly constantly.' In 2015 that figure was a slightly less alarming 24 percent.

What does all this mean?

What's the takeaway here? That depends on who you are. If you're a Facebook exec, these numbers probably signal you need to consider how to prevent your platform from becoming the province of batty aunts and late-to-the-online-party grandparents (though the fact that rising star Instagram is owned by Facebook should give the company some comfort). Media and other companies dependent on Facebook should also take note.

If you're a parent worried about how much time your kids spend staring at screens, the fact that half the nation's youth are constantly fiddling with their phones is unlikely to calm your anxieties. Some sociologists suggest you are right to fret. While the impact of phones on kids is still fiercely debated, a striking rise in teen anxiety and loneliness closely coincides with the surge in smartphone use among young people.

Teens themselves, meanwhile, are probably not too shocked by these figures. Nor is it likely news to them that that almost a quarter of respondents (24 percent) said social media has a negative impact on their lives, with 27 percent of those social media skeptics citing online bullying as the main problem. In fact, recent in-depth interviews with young people about their relationship with their devices found a deep ambivalence about time spent online, with many kids actually saying they wanted help setting healthier boundaries.

The bottom line, then, for those building Facebook reliant-businesses is not to put too many eggs in this one increasingly rickety-looking basket. For everyone else the message is one you've no doubt heard a few times already -- it's high time you and your family start being thoughtful and intentional about your screen time.

If you're looking for a way to begin getting a better handle on your online life, here's one suggestion: try a month-long digital declutter.