What is the incidence of autism?

Autism was conceived as a very specific disorder almost always associated with mental retardation, but quite severe. The estimates there were four or five per 10,000 kids, so maybe one in 2,000 kids, had the disorder, but what has happened is that the conceptualization of the disorder has gotten quite a bit broader to encompass kids who have specific social deficits. It includes a general pattern, but is not necessarily mental retardation, and so there are more of those kids. We do not know if having a broader definition accounts completely for this rise in number, or whether there actually are more kids with autism or autism-spectrum disorders. Now, autism is seen much more as a spectrum rather than just one single disorder. Part of the confusion is who exactly is in that spectrum. Where do you draw the line? So, that has meant that their estimates are anywhere from one in 100 to one in 200, which I think is the most commonly accepted prevalence rate.