I tutored a young autistic man in college and he was almost non-verbal. He could communicate through speech, but only in monosyllables and with great difficulty and stuttering. That was the only definition of autism I understood at that time, and he was considered better off than many.

A few years later when I learned about Asperger's because my sister got diagnosed with it, I went to get evaluated myself and after sitting down with me once, they said I'm not autistic.

I'm about 99% sure I would be placed on the autism spectrum today.

I don't know whether it's good or bad that the diagnostics / definition of autism seem to be broadening — that's above my pay grade. But you can't deny people who weren't considered autistic 30 years ago are today, and so to compare autism rates which measure clearly different levels of capability is pretty useless.

In order to compare rates, we would need a consistent set of diagnostic criteria.