I left an important one out, which I was pretty sure was wrong, but I needed to research it a bit more.
So I would tell you either go back to the 1989 schedule before this whole mess happened or go to Finland's schedule, Sweden's schedule, Norway's schedule and use theirs. Because their autism rates are one tenth of ours.
He must mean their rates of identified autism are one tenth of what they are in the US. I don't like it when people don't make that clarification.
But let's see what a quick search of the literature has to say.
One study in the town of Karlstad, Sweden (Kadesjö et al. 1999) had found the prevalence among 7 year olds to be 1.21%. I'll let Lorna Wing summarize why this study is of interest:
Kadesjö et al (1999) report a study in Karlstad, a Swedish town. Although this was small scale it was very intensive (over 50% of the 7 year old children seen and assessed personally by the first author). The study found a prevalence for all autistic spectrum disorders for all levels of IQ, of 1.21%!!! Children were followed up four years later and had the diagnoses confirmed.
That's not all, though. You have, for example, Arvidsson et al. (1997), a study that set out to identify "all individuals with severe degrees of autistic behaviour." They found a prevalence of 31 in 10,000 among 3 to 6 year olds. This is more like half of the consensus prevalence in the US.
Then there is Gillberg et al. (2006) which finds a prevalence of 20.9 in 10,000 for autistic disorder, and 32.9 in 10,000 for "other ASDs." That's 53.8 in 10,000 total.
There are several other studies from Sweden we could look at, but I think the wrongness of Handley's claim has been clearly established just with the ones mentioned.
Mattila et al. (2007) found a prevalence of 25 in 10,000 for Asperger's Syndrome alone. This is actually higher than what the prevalence of Asperger's in children is normally found to be.
An older study, Kielinen et al. (2000), finds a prevalence of 20.7 in 10,000 among 5 to 7 year olds. This is lower than the US consensus prevalence, but it's only 1/3rd of it, not 1/10th. Additionally, note that 50% of the children had IQs below 70. This is different to what you see in California DDS, for example.
The most recent epidemiology from Norway is a bit old, and here we do see that the prevalence is similar to what it traditionally was for Kanner autism. For example, Sponheim & Skjeldal (1998) find a prevalence of 4 to 5 in 10,000 for 3 to 14 year olds, using ICD-10 criteria.
However, there's a recent screening of 7 to 9 year old children using the ASSQ. That's Posserud et al. (2006). It finds that 2.1% of children were high scorers in the ASSQ when both teacher and parent questionnaires were considered. (It was 2.7% if they considered teacher forms only, as some parents declined to participate.) That seems high.
Unfortunately, Posserud et al. don't tell us how many were confirmed to be diagnosable with ASD after the screening. There's an update of that study, Posserud et al. (2009). I wish I had a copy. All I know is that the ASSQ is found to have a sensitivity of 0.91 and specificity of 0.86, which appears good.
In any case, JB Handley's assumption is kind of simplistic even if we only consider the country of Norway, as it ignores all the issues involved in identifying autism.