I loved this infographic and just wanted to re-share it. But I also wanted to point out the author's post has a great explanation of that "tween" category, 13-15, who so often feel left out of YA completely nowadays. See also, the School Library Journal, "Middle Grade is too Young, YA too Old. Where are the Just- Right Books for Tweens?"
I've taught The Outsiders in 7th English Language Arts, to 12- and 13-year-olds, and Hunger Games to 13- and 14-year-olds, and some were not ready for either book, while some devoured them both with no problems. Every child is different.
I find it interesting, as well, that The Outsiders, which kinda got the whole YA thing rolling, has smoking, drinking, gangs, gang violence, arson, homelessness, and death.
But by the time you get to now, included in the list is Aru Shah, by Roshani Chokshi, which (I've read it, don't worry) I'd clearly label as firmly middle grade, not YA at all. It's super gentle compared to The Outsiders or it's rival, Hunger Games.
But it is indicative of this yawning gap between MG and YA that feels like the Grand Canyon when you're in it (I have a 15-year-old).
So when writers ask, is my manuscript MG or YA? Or, can I have a 14-year-old protagonist in a YA book?
I totally understand their confusion.
But I think these labels, MG / YA are fluid, depending on expectations and norms of the moment, and I love how this graphic shows that.