A pair of studies on autism rates show that somewhere around one percent of all U.S. children currently have an autism spectrum disorder (ASD). The rate is even higher among 6 to 11 year olds and among boys.

Among all children aged two to 17, one in 100 currently have an ASD, which is considerably higher than the previously estimated rate of  one in 150. There was an 100 percent increase in parent-reported ASD rates compared to the 2003.

One possible explanation for some of the increase is the expansion of the ASD classification within the public schools to include not only full-blown autism, but also milder forms of ASD such as Pervasive Developmental Disorder and Asperger's Syndrome. But it is difficult to believe that this accounts for the entire increase.

One possible answer is the Hepatitis B vaccine, which also contained 25 micrograms of mercury containing thimerosal. Only 8 percent of infant children received the Hep B vaccine in 1992, when that birth cohort showed an ASD rate of 60 per 10,000.

By 1994, the number of children receiving Hep B vaccine had reached just 27 percent -- and the cohort showed an ASD rate of 66 per 10,000. The Hep B coverage rate rose to 82 percent by 1996, when that cohort's ASD rate exploded to around 100 per 10,000, or one in 100.