A massive comprehensive study in South Korea found an overall rate of 2.6 % children with autism or 1 in 36 children. The usual rate cited for autism is 1 in 66 children.
This is the first comprehensive study of an entire population and suggests that autism may be even more prevalent than we first thought. Our current system of diagnosis relies on parents, teachers or doctors raising concerns and having the child tested, which means that many children are probably slipping through the cracks.
Further study is needed in order to understand the numbers and follow up studies are planned for India, South Africa, Mexico and Taiwan. No mention of plans for European countries, the United States or Canada.
If we could ensure that every child with autism received a diagnosis, our understanding of the condition would certainly improve, which might lead to less stigma and more effective treatments.