The epidemiology of autism is the study of the incidence and distribution of autism spectrum disorders (ASD). A 2012 review of global prevalence estimates of autism spectrum disorders found a median of 62 cases per 10,000 people.In contrast, a 2016 review of global prevalence estimates of autism spectrum disorders found a median of 18.5 cases per 10,000 people. However, there is a lack of evidence from low- and middle-income countries.