Why has autism rates remained the same since thimerosal has been eliminated from vaccines in 2001?

Because vaccines: With thimerisol don't cause autism. There is a genetic set-up for autism, just like there is for diabetes & asthma. Unfortunately, there are many genetic set-ups for autism, epigenetic factors cause changes in function but not structure of fetal genes (e.g., some viruses & toxins).. Environmental triggers precipitate the symptoms of diabetes, asthma & probably autism, but the ? Is which ones.

Actually gone up : The rate of autism was about 1 case per 150 children in 2000, and is now 1 per 88 (in boys it's 1 in 54). The inciting cause(s) is multifactorial as dr fricke stated. One single agent of etiology is not supported by research.

Autism: According to the cdc, no association between MMR and autism. There was a theory that the thymersol preservative was contributing to autism, but the autism rates rose even after the thymersol was removed. It is a major mistake to not have one's kids fully vaccinated. The cause of autism is not known, although recent studied suggest a relationship with fever during pregnancy.

Easy: Because the chemical has nothing to with autism.

They have increased: It is likely that disorders on the autism spectrum may differ in cause and in fact may really be many different diseases. Within the last several years the autism rate has risen from 1/150 to 1/88. Mercury may be discovered to be a factor but now there is no definitive research to support it. Immunization causing autism was debunked because that research was flawed and results manipulated.