Why would the UK have the highest rates for autism?

Perhaps the uk has more of a 'problem' with autism, because we are much less expressive as a culture than others?
Perhaps more autistic people in say, italy, get by because their more expressive nature makes reading people easier?
if we score autism out of 10 with 1 being mild and 10 being really autistic, maybe a majority of 1-5 level autistics can get by in an expressive country, but the uk, only 1-3 level autistics can get by to the extent that they are not diagnosed.

Im not saying that is the case, but i have an italian colleague who i find slightly easier to read.

I was told by foreign colleagues and students that I was particularly easy to understand. I was always aware when talking to non-native speakers, to enunciate clearly and avoid slang and idiom.

If your thesis is correct, autistic people must have a particularly bad time in Japan, with the Japanese reputation for extreme reserve, precisely nuanced etiquette and insistence on collective conformism

I was told by foreign colleagues and students that I was particularly easy to understand. I was always aware when talking to non-native speakers, to enunciate clearly and avoid slang and idiom.

If your thesis is correct, autistic people must have a particularly bad time in Japan, with the Japanese reputation for extreme reserve, precisely nuanced etiquette and insistence on collective conformism

Ha, ha!

Hey, snap! High five etc. 

I read ‘Convenience Store Woman‘ by Japanese author Sayaka Murata. The central character seems to be autistic, and is the focus of her family and acquaintances efforts to make her live a more acceptably 'normal life', though she does no one any harm whatsoever.

The book ‘Convenience Store Woman’ explores that very thing. Being autistic in Japan. Implied autistic anyway. You have to be either graced with a version of autism where you are immune to feeling pressured or you suffer excruciatingly. Two contrasting characters show the ways this can go. 

I was thinking specifically about body language.   But i agree that maybe the high rate in japan is down to their rigid social rules.