Cynthia Nevison and William Parker, Journal of Autism and Developmental Disorders, March 19, 2020
County-level ASD prevalence was estimated using an age-resolved snapshot from the California Department of Developmental Services (DDS) for birth years 1993–2013. ASD prevalence increased among all children across birth years 1993–2000 but plateaued or declined thereafter among whites from wealthy counties. In contrast, ASD rates increased continuously across 1993–2013 among whites from lower income counties and Hispanics from all counties. Both white ASD prevalence and rate of change in prevalence were inversely correlated to county income from birth year 2000–2013 but not 1993–2000. These disparate trends within the dataset suggest that wealthy white parents, starting around 2000, may have begun opting out of DDS in favor of private care and/or making changes that effectively lowered their children’s risk of ASD.
Statewide California ASD Prevalence Trends by Race/Ethnicity
ASD prevalence statewide (summing over all 58 California counties) reached 1.5% by birth year 2013 in the DDS dataset. Highest prevalence occurred among black children (1.8%), followed by Asian (1.7%), white (1.4%) and Hispanic children (1.2%). While ASD prevalence among all race/ethnicity groups increased more or less continuously from birth year 1993–2013, a discernible flattening in the growth trend occurred around birth year 2000 for all groups except Hispanics and was particularly evident among whites. The flattening persisted only a few years for blacks and somewhat longer for whites and Asians, but by the mid to late 2000s all groups had resumed some degree of upward growth in ASD prevalence.