I would say on this side of the pond, the adolescent’s use of Fb has dropped dramatically especially among the younger kids. As the father of three kids ranging from the 20 to 30 - they no longer use Facebook, and neither do most of their friends. Surprisingly, when I mention the privacy aspect, that doesn’t seem to be an issue at all - they tell me that most people their age are not the least bit worried about the reams of data Google, Fb, et. al., are collecting. They don’t seem to like the fact that their parents are all on Fb. So - they’ve moved to Instagram and Snapchat. At least that’s their story and they’re sticking to it.
I’ve recently talked a couple of clients with websites into opening up Facebook accounts. Reason being that they can then easily be tagged - and then their website discovered. For example, a guy with a home remodeling business was not on Fb for the longest time, and when people would ask for recommendations, it was impossible to tag his company. Now, it’s a piece of cake.