[yummyfajitas]

Very true. We have little good information on this topic, and the original article is wrong - we don't have good evidence that 40 hours is a universal cap.

Most of the data supporting 40 hours/week applies to manufacturing and construction, and is old. Contemporary data (of which there is very little) suggests 60, and again problems of comparing knowledge workers to construction arise.

If someone has good data, I'd love to see it. Until then, stop citing 40 hours/week as peak productivity.