The stats can be tricky for several reasons.
- There are a LOT of things for which people can be vaccinated, and the focus can vary around the world depending on what diseases are prevalent. Most charts focus on either DTP3 or something specific. I have not found a chart that captures everything going on in a particular place.
- I can't tell if the full spectrum of autism diagnosis is the same everywhere. In other words, some places could show more cases of autism or an accelerating/decreasing prevalence based on how they establish the range of the spectrum and how many personnel are available to diagnose. It's clear that in the United States, that method and ability to diagnosis are huge factors. The variance of ASD rates between states is crazy simply because of the difference in resources to diagnose and treat.
- It's absolutely true that autism have been rising significantly. However, keep in mind that autism wasn't even in the DSM until the early 80s, so there was not autism data before that. Since then, as the definition/understanding has expanded, obviously the diagnosis has grown. In addition, many people who have once been diagnosed with mental illnesses are now considered to be on the spectrum. (See "The Real Reason Autism Rates Are Up In The United States" for more information.) A number of years ago, a study was released showing that certain states in the US had much higher rates of child abuse. That wasn't actually true. Abuse rates are pretty consistent - if we define abuse the same way in every state. Poverty can appear to rise and fall in the US not because people's financial situations change, but because we change how we define poverty. In the same way, autism is rising - but that's obviously going to happen as we continue to broaden the diagnosis and focus on diagnosing.
So, I thought I would take a different approach this time and look for what is happening around the world. In spite of the caveats I mentioned earlier, there are trends we can observe. I will be using data from OurWorldInData.org. They compile data from other organizations and make it understandable; they also allow downloads of their charts for use in presentations :)