In 2003, Jakob Nielsen reported that, on average, a usability redesign could increase desired metrics by 135% (based on a study of 42 site redesigns). Fast forward to 2008, Jakob reports in a similar study that gains have dropped to 83%. Why? Usability has become a standard online, making the possible impact smaller than 5 years ago. And it seems that usability budgets have not increased.
As someone working in the User Experience field, there's no doubt that there's been a surge in UX people and work in the last decade. Entire career paths have been dedicated to the practice of user-centered design: Information Architects, Interactive Designers, Usability Analysts, and many others. Non-profits and government agencies alike have taken the lead from their commercial peers and invested in audience research and usability improvements.
This is a vast improvement from earlier generations websites. Ten to fifteen years ago, websites were growing organically and usability was hardly a factor in design. Today, usability has become part of our standard rhetoric.
Looking forward to what the next decade brings in the UX field.
JN's 2003 ROI report
JN's 2008 ROI report