Assuming you have an autistic child or relative, your personal experience does not constitute the research necessary to learn whether the incidence is growing or stable. I can assure you that in the early 70s when I was in graduate school, the diagnosis was common enough that every small town had several children in treatment.
At that time my professors were going against the textbooks to claim that the problem included people with a wide spectrum of severities.
It is a funding issue on the grand scale...it should never be one for the true autistic child or his family but it can be if their district isn't geared to the special education funding machine (that will also result in over diagnosis by it's industrial self perpetuation.)
In order to properly treat this, the system exaggerates the need.