In 2010, overall estimated ASD prevalence was 14.7 per 1,000 (1 in 68) children age 8 years (U.S. Centers for Disease Control and Prevention [CDC], 2014).
Reported prevalence rates have been rising steadily since the 1960s, and it is not completely clear to what extent this is reflective of a true increase in prevalence or increased awareness of ASD and its diagnosis. For example, studies with access to both school and health records have found substantially higher rates than those with access to health records only. Some researchers believe that the increased prevalence of ASD may reflect changes in practices for diagnosing autism. For example, the likelihood of receiving a diagnosis of ASD increased as children with an earlier diagnosis of intellectual disability (ID) subsequently acquire the diagnosis of ASD (King & Bearman, 2009; Shattuck, 2006).
It has been established that prevalence varies by gender and race/ethnicity. The CDC study found that prevalence was 18.4 per 1,000 (1 in 54) among males and 4.0 per 1,000 (1 in 252) in females. Prevalence among non-Hispanic white children (12.0 per 1,000) was significantly greater than among non-Hispanic black children (10.2 per 1,000) and Hispanic children (7.9 per 1,000). Given that there are no clearly documented differences between these groups in terms of risk factors for ASD, disparities in prevalence estimates suggest under-identification among Hispanic and non-Hispanic black children. Insufficient data were available for children of Asian/Pacific Island descent.