A while back, when I was discussing the rate of autistic children increase with my sister, a PhD at UC Davis, and she pointed out that the result is fairly inconclusive due to the fact that the diagnosis for autism is getting better, thus able to identify more children diagnosed with autistic. Well, it was a reasonable argument.
On Jan 7th, 2009, UC Davis M.I.N.D. Institute study shows California's autism increase not due to better counting, diagnosis, since 1990. So how can we answer to that? The study shows the increase is "seven- to eight-fold"! If this does not raise an alarm in our government, I do not know what else.