Autism and Developmental Disabilities Monitoring Network
The Autism and Developmental Disabilities Monitoring Network (ADDM) is a group of programs funded by CDC to determine the number of people with autism spectrum disorders (ASDs) in the United States. The Network's goal is to provide comparable, population-based estimates of the prevalence rates of ASD in different sites over time. The Network data can provide a population-based description of the characteristics of ASDs; determine differences in ASD prevalence among different population groups and/or geographic regions; and monitor trends in ASD prevalence.
http://www.cdc.gov/ncbddd/autism/addm.html and related web pages.