You do know the increase came from uniformity in the criteria for diagnosing autism, right? That’s why there’s nothing before the 70s. There wasn’t some magical increase in the number of autistic people; there was simply an increase in diagnoses. They now know that people learn to mask their autistic behavior and people are being diagnosed later in life. It’s not all kids in your graphic.

I’m all for the spread of information but at least make sure that information is factual and stands up to scrutiny.