Why an Increase?

Why would anybody think there might be an increase in autism?

When autism was first described by Dr. Kanner, he said that this is an extremely rare disorder. At the time autism prevalence was estimated at about 1 in 10,000. The most recent CDC estimates are about 1 in 150. If the word 'autism' still retains its original meaning and these estimates are even remotely accurate than there is a huge increse in autism. Moreover, there have been a number estimates inbetween those two and one may notice that estimates of autism prevalence have steadily increased over time.

Also, the number of children enrolled in special education in California with a diagnosis of autism has been on a steady increase over the last 17 years, ever since 'autism' was introduced as a separate cathegory by the Department of Developmental Services in 1991.