I can anecdotally tell you that rising diagnoses of autism spectrum disorders has a lot to do with naming them. I've worked with upwards of three thousand children (likely more), aged three to twelve, from the early seventies to a couple years ago.

In 1972, we had one child tentatively diagnosed as autistic. We had several other children diagnosed with the ubiquitous FLK disorder (for those not in the know - FLK = Funny Looking Kid, psychiatric meaning, we know something's wrong, but have no idea what), who I'd bet would be called autistic today. Some of the children diagnosed as 'hyperactive' and dosed to the eyeballs with Ritalin in the eighties would be called autistic today. I am sure of that. In the nineties, more children were diagnosed with autism spectrum disorders, and certainly some of them would have had a different label applied in the previous decade.

The last two 'diagnosed as' children I worked with were both diagnosed with Asberger's Syndrome, but two more different from each other children could not be found. I found it difficult to reconcile the symptoms of one with those of the other.