Usability ROI Declining, But Still Strong

It's been a while since I checked on one of the elders of usability, Jakob Nielson. Checking his man's web site (Alert Box) I came across an interesting post on the ROI of usability and how it's still a great deal for $ spent vs $ earned/saved (spend 10%, gain 83% by Jakob's calculations.) The article also shows that the big gains of the last 6 years have been achieved and now it's a matter of incremental upkeep or initial design. Math was not my best subject, but the argument that increasing conversion rates (somewhat the domain of experince design) is more desirable (and less expensive ) than increasing unique visitors (the domain of advertising.)