One difficulty with this is the number of teens with social media accounts that have a false age. Most of our friends' kids and many of my nieces and nephews f

One difficulty with this is the number of teens with social media accounts that have a false age. Most of our friends' kids and many of my nieces and nephews fall into that category, some because they got an account before age 13 and lied, or were older than that and lied to have access to some forums, or just because they just wanted to pretend to be older (my own daughter is an introvert with good sense and isn't on social media). I suspect that Google and Facebook are well aware of this internally.