: There's a lot of debate about this... There are a lot more children being diagnosed with autism for 2 main reasons:
-In the last 5-10 years, a lot more of the high functioning end of the spectrum has been diagnosed. That makes up a *huge* amount of the increase. Prior to this, these were the "quirky", "weird", "loner", "antisocial" kids. Now, a diagnosis is being put to the symptoms. 15-20+ years ago, my child with autism would not have been diagnosed with autism...that diagnosis was reserved for people with much more severe cases than my son is. There is also more awareness now, so when a child is showing signs of not developing appropriate social skills and having other symptoms, they are diagnosed pretty early on instead of getting to adulthood with no diagnosis. When you say there are a lot of children around you who are autistic, that is because awareness has increased so much that you know what autism, especially HFA, looks like. 20 years ago, when someone said the word "autism", it typically brought up images much more severe than what people think of today...
To find the true number though, we really would have to go through and see how many undiagnosed ASD adults there are. I believe there was a study done recently that did just this in another country. They basically went door to door and screened adults, and in the end, they found out that roughly 1 in 56 adult males and 1 in 200 adult females in the England met criteria for ASDs. That is roughly what the diagnosis rate in children currently is as well.
Here is a fantastic article about the so called "epidemic". http://www.iancommunity.org/cs/under...rch/prevalence
ETA: Also, prior to 1990, the federal government did not recognize autism as a disability for special education, and therefore, children in public schools typically did not carry that diagnosis, or it wasn't one that was frequently encountered in the schools like it is today where there are a lot of services offered and reimbursed for through the NCLBA.