Secret Benefits of Accessibility Part 1: Increased Usability
http://www.sitepoint.com/article/accessible-usable-website/

Moss, Trenton
SitePoint
2004

Abstract:

Web accessibility has so many benefits that I really do wonder why such a large number of Websites have such diabolically bad accessibility. One of the main benefits is increased usability, which, according to usability guru, Jakob Nielsen, can increase the sales/conversion rate of a Website by 100%, and traffic by 150%.