The Australian Bureau of Statistics (ABS) in 2022 state:

• Autism prevalence was higher for people aged under 25 years (3.1%) than people aged 25 years and over (0.3%).
• Almost three quarters (73.0%) of Autistic people had a profound or severe disability.

The Australian Psychological Society in 2025 state:

• Less than half (45.1%) of Autistic people aged 15-20 complete Year 12, and just 5.2% attain a Bachelor’s degree, compared to 35.3% of people without a disability.  
• Workforce participation is alarmingly low, with only 50.2% of working-age Autistic Australians actively engaged, and a mere 11.4% employed full-time.  
• Autistic adults are 2.5 times more likely to experience depression than the general population and face higher rates of homelessness, discrimination and social isolation. 

As shown above, diagnosed children make up the largest proportion of all autistic persons and their life outcomes are depressingly limited.

There is also some data on the prevalence of Intellectual Disability and Autism in the U.S., with the CDC reporting approximately 40% of autistic children also having an intellectual disability (source: Is Autism an Intellectual Disability? Key Differences – ScienceInsights).

However, there is currently a distinct lack of comprehensive, centralized national registry data tracking the exact rate of this specific dual diagnosis across Australia. According to the Victorian Dual Disability Service, “25% to 40 % of people with ID have Autism, [and] 40 to 70% of people with Autism have ID (borderline IQ also common)” (source: https://www.vdds.org.au/wp-content/uploads/2025/04/Autism-and-Co-occurring-Mental-Disorders.pdf). Bourke and colleagues (2024) suggest that the NDIS funding model has contributed to an increase in formal diagnoses. (source: https://pmc.ncbi.nlm.nih.gov/articles/PMC11145759/ )

Data Sources: https://www.abs.gov.au/articles/autism-australia-2022 and https://psychology.org.au/insights/unpacking-the-national-autism-strategy