Research does not say that people produce more when working 40 hours per week

Article is focused on the academic world so doesn't talk about interruptions, meetings, and quiet time.

If you work in an open-plan office the 10 hours you do at night, at home, and on the wkend can be the most productive.

I've had months where I put out more real fires on a kayak, on vacation, than at my desk; people bother you when you're at a desk but they can't get to you on the water.

> the point of productivity inflection is just about 40 hours per week

To me, that does seem to support the claim “research shows that 40 hours per week is the best”. I don't know who's claiming that overall output goes down the minute you hit 40, that's obviously exaggerated, so why take it so seriously? There's strong evidence that productivity starts to decline somewhere around 40ish, and it obviously varies by individual and situation.

I think the more common, and more correct claim is that 40-ish is optimal, rather than anything above 40 is a negative return.

That bit of data he referenced is for munitions workers doing a low-skill monotonous job - easy to measure productivity. Who would expect to produce solid high quality thought output for 40 or 50 hours a week? I'd be surprised if most academics & programers managed more than 15 hours of conceptual work in a week, the rest we fill with coffee & lunch, browsing the web, talking to people, and loads of other stuff that doesn't require much thinking.

The author's completely right about many of his points; this just isn't clearly defined or unambiguously supported by data. There are obviously some people out there rationalizing and mis-presenting the evidence in favor of a 40 hour work week. As with all studies, there are people who summarize incorrectly and decide that weak evidence justifies a hard line decision. But why get twisted over the worst arguments? Let's discuss the strongest arguments instead.

Do we need data to support the idea that 8 hours is enough? Productivity is only a tiny part of the equation, so this debate is academic. Why are we obsessing over unmeasurable productivity and ignoring labor & poverty issues? Do you need data to prove that when you work 12 hours a day, you physically can't have much life outside of work? The idea of an 8 hour work day is meant to work for everyone. It's guaranteed to be conservative, because it has to be good enough for teenagers as well as people near retirement, for single people as well as parents, for everyone.

Any creative work does not follow a timeline. Butt in the seat means nothing. In fact, the opposite -- the more relaxed and freeing the structure of work, the better the output.