Recently, there have been several announcements about the number of people who have autism spectrum disorders (ASDs). These numbers, which are widely reported by the media, keep going up, causing both interest and alarm. In late 2009, more new figures were released -- 1 in 110, 1 in 100, 1 in 91 -- and these again showed an increase, even over figures from just a few years ago.
Where are these numbers coming from, and how were they calculated? How are we defining autism spectrum disorder, and how many people have one according to that definition? Do more and more people truly have ASD, or are we getting better at identifying the condition? Are we counting everybody, or are some people being missed? We look to the latest studies on autism rates to find out.