7. Increasing Prevalence Autism, strictly defined 4-6 in 10,000 prior to 1980’s (Lotter 1967) 16-20 in 10,000 today (Chakrabarti & Fombonne 2001) Autism spectrum disorders 10 in 10,000 in 1990’s (Bryson et al 1988) 60-70 in 10,000 today (Chakrabarti & Fombonne 2001)