Here's a link to the study:<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0011551" rel="nofollow">http://www.plosone.org/article/info:doi/10.1371/journal.pone...</a><p><i>A compelling argument has been made that the positive associations between SES and ASD prevalence that have been observed likely are due either in part or entirely to ascertainment bias [22]–[24], [30], [31]. For example, it has been suggested that “more parents of high social class families [have] the necessary information and financial resources to find their way to the specialized facilities” [23] and “a knowledgeable and determined parent of an autistic child [is] more likely to obtain an informed diagnosis” [24].</i><p>Interesting to explore whether the diagnosis is resultant from "better" (higher paid?) doctors' opinions or if the frequency of ASD really would be higher among that strata of socioeconomic status.