It did, but the diagnosis criteria was expanded years ago and more cases have been diagnosed since. This does not explain all the increases, but it does explain some.
"This does not explain all the increases, but it does explain some."
I'd be more interested in finding the reason for the rest of the increase than in a lot of things we spend money on.
What a tragedy it would be if the misery caused by autism were due to mercury, and we just didn't bother to look.