Some articles mentioned something along those lines, but they seemed more written with an axe to grind, and more from the states. The rich part I can't speak to, but autism is just plain more common in whites than blacks, not underdiagnosed, to my understanding. Ed girlfriend used to work with the autistic, and in a heavily multicutural city where white people are not a clear majority, nearly all the severely autistic she worked with were white/iranian/middle eastern/ other whitish varieties it seemed, hardly any black or asian.