Comment by Seb-C

If you ask any high-functioning or late-diagnosed autistic person who knows about the topic, you can bet that he will tell you his family (parents and grand-parents included) shows the same signs of autism, but that they do not wish to aknowledge it or be diagnosed. These people will never be included in any proper statistics because they see themselves as "normal" or "just a little different", despite being widely known as "weird".

Previous generations didn't grow up with all the comfort that we have today, such as games, internet and technology, and thus didn't have as many ways to isolate themselves in more comfortable hobbies. Because of this, they could develop stronger masking skills, which helps them a bit more than current generations, but does not fix the problem and made the understanding of it more difficult.