“Only 33.7 percent of working-age adults with disabilities are employed, compared with 72.9 percent of people without disabilities, according to the Institute for Community Inclusion, based at the University of Massachusetts. For working-age adults who have intellectual and developmental disabilities, the number plunges to just 16 percent.”
http://www.philly.com/philly/columnists/ronnie_polaneczky/intellectual-developmental-disabilities-employment-falling-off-the-cliff-part-3.html