Several studies are underway to measure the real impact of Universal Design - beyond anecdote and case studies. Universal Design in Practice ( UDiP) is one such project. Housed at Georgia Tech and funded by NIDDR it is officially titles, This 3-year NIDRR-funded project is officially titled "Analyzing Universal Design Resource Needs for practitioners in industry and government."
For more information see:
http://www.isye.gatech.edu/lhci/udip/contents/introduction.php