The prevalence of autism diagnoses has increased drastically since 1966. There was a significant spike of autism in the United States between the years of 1983 and 1990. Autism affects four times as many males than females with a prevalence of 1/110 in the United States. While it can be suspected that the rise in autism can be considered a result of reclassification, there haven’t been any changes in prevalence of mental retardation, speech/language impairment, or traumatic brain injury. This rise in prevalence is unique to autism, which suggest that the increase of autism is real.