From Science Daily:
Autism May Be More Prevelant Than Previous Estimates
February 8, 2007
Science Daily — The Centers for Disease Control and Prevention (CDC) reported findings today from the first and largest summary of prevalence data from multiple U.S. communities participating in an autism spectrum disorder (ASD) surveillance project. The results showed an average of 6.7 children out of 1,000 had an ASD in the six communities assessed in 2000, and an average of 6.6 children out of 1,000 having an ASD in the 14 communities included in the 2002 study. All children in the studies were eight years old because previous research has shown that most children with an ASD have been identified by this age for services.
For decades, the best estimate for the prevalence of autism was four to five per 10,000 children. More recent studies from multiple countries using current diagnostic criteria conducted with different methods have indicated that there is a range of ASD prevalence between 1 in 500 children and 1 in 166 children. The CDC studies provide information on the occurrence of ASDs in fourteen communities in the United States.
Read the rest here.