I read a lot of YA and the trend seems to be toward older teen protagonists, at least 16 or older with a few being in their twenties. What I’ve noticed more and more is that the age range seems to be getting narrower and narrower. When I was a teen (which wasn’t that long ago) there seemed to be a broader age range (anywhere from 14 to 19 or so). But now I’m seeing more books with MCs between 16 and 18 but rarely outside that range. And younger and younger readers are reading these books (I know ten year olds who are reading hunger games, twilight, etc.). This all stuff that I’ve noticed lately.
On a side note, my MC of my current WIP is 17. Most of my other stories also have MCs between 16 and 18 generally, with most being either 16 or 17.