There are several ways to estimate the number of children with ASD. This estimate is referred to as prevalence, a scientific term that describes the number of people with a disease or condition among a defined group (or ‘population’). Prevalence is typically shown as a percent (e.g., 0.1%) or a proportion (e.g., 1 in 1,000).
ASD prevalence estimates from the following four data sources are presented on this webpage:
Prevalence estimates can vary by type of data source because data are collected in different ways.
DOUG NOTES:
Hence:
Why does the top graph show a decrease in the number of Montana students with autism from 2010 to 2011, while the bottom graph shows an increase for the same time span?
Because in 2011, the federal government changed the order of "primary" disabilities in how they rank the "order" of disabilities in child count. The ACTUAL number of students with autism didn't decrease, just those who had a primary disability of autism in 2010, but not in 2011. So the same kid with autism might be counted (or not counted) differently from 2010 to 2011, even though their autism and autism identification did not change, because they no longer had a "primary" disability of autism.
Graphs from the OPI Montana Autism Education Project show ALL public school students with autism, not just those who have a "primary" disability of autism. We think that is the truest way to show the number of students with autism.
Like Abraham Lincoln said to Mark Twain, "There are three types of lies: lies, damned lies and statistics."
