However, this would support emerging data that suggests older parents to higher incidents of children with autism. Further studies also show correlation of fertility drugs and IV birth to autism, which older couples are more likely to use than younger fertile couples. So these pockets in white affluent areas so not surprise me as white affluent couple wait to have children and use fertility drugs and IV at a higher rate than the general population.
Your point may be tied with what I heard (see post 12) since people with higher IQs may tend to wait later in life to have children, and may tend to use IVF or other similar procedures more often. It would be interesting to see a detailed “census” of autistic families.