[cobaltblue]

If you include thinking about work, then even work-from-home people could reach the 50+ figure relatively easily since you include weekends and trying to get to sleep. But then you might easily get into low numbers of hours per week, 15-30, if you subtract things like spending some large % of your time doing non-productive non-work (happy hours, lunches not at your desk, watercooler talk, browsing HN) even though you're at work.

Work time should generally only be the time between clock-in and clock-out. For professionals that are freed from clock-in-clock-out, I think they would still clump around that 40 hour figure if you made them clock-in-clock-out for the data rather than for the pay.