It's certainly both. The definition has literally expanded (now including Asperger's), but with more awareness it's more likely people who are borderline autis

It's certainly both. The definition has literally expanded (now including Asperger's), but with more awareness it's more likely people who are borderline autistic will be able to get diagnosed. This all makes it very hard to answer the question "are more people today autistic than 50 years ago?"