Following up on the links you gave me on Twitter.

These two fall into the awful pop-sci writing category:

http://www.economist.com/blogs/freeexchange/2013/09/working-...
“And it seems that more productive—and, consequently, better-paid—workers put in less time at the office”
“So maybe we should be more self-critical about how much we work. Working less may make us more productive.”

http://www.oecdobserver.org/news/fullstory.php/aid/3841/Prod...
This points out that the average worker in Greece works more hours than the average worker in Germany.

These are clearly confusing correlation with causation, and I doubt very much that any of the actual researchers involved, as opposed to op-ed writers, would even imply that if only the workers in Greece would ease up a bit, they would get the productivity of Germany. Would you make that statement?

This one covers a lot of actual research, but mostly on the relationship between overtime and worker health and safety:
http://www.cdc.gov/niosh/docs/2004-143/pdfs/2004-143.pdf

I don’t find much to argue with here. I don’t dispute the premise that working very long hours can have a health impact in some cases.

It was interesting to see the clear step function in the leading graph of average annual work hours by country with the US at ~1850 as the highest of the mostly-western countries, but Thailand, Hong Kong, and South Korea in a distinctly different class, topping out at ~2450 for South Korea. That made me smile, because one of the Samsung people we work with referred to us at the Oculus Dallas office as “honorary Koreans” because of how hard we work. I do note that the chart in the Economist link with more recent data has them still at the top, but down to ~2100 hours in 2012.

A couple interesting (unrelated) counterpoints from the studies:

Sokejima and Kagamimori [1998] observed a U-shaped relationship: as compared with 7 to 9 hours of work per day, higher risk (for cardiovascular problems) was associated with both shorter hours (less than 7 hours a day) and longer hours (more than 11 hours a day)

Nakanishi et al. [2001b], however, published the opposite results: white collar workers reporting 10 or more hours of work per day had a lower risk for developing hypertension when compared with workers reporting less than 8 hours of work per day

There are some small bits directly discussing performance:

3.2d Extended Work Shifts and Performance
Two laboratory studies reported deterioration in performance with extended shifts.
In contrast, four field studies reported no differences in their performance measures during extended shifts.

3.4b Very Long Shifts and Performance
A study in Ireland by Leonard et al. [1998] reported declines in two tests of alertness and concentration in medical residents who had worked 32-hour on-call shifts. They reported no significant declines in a test of psychomotor performance or a test of memory. A New Zealand survey of anesthesiologists linked long working hours to self-reported clinical errors [Gander et al. 2000].

I glanced at the other links, and they look potentially interesting, but non-responsive as far as giving actual data showing that working more than 40 hours a week makes you less productive.

Perhaps there is confusion about my position, so let me clarify:

Average productivity per hour will decline with extended work. The highest average hourly productivity could be with shifts as short as six hours for many people; I have no particular thoughts on this, as I have never had reason to care to optimize it. An assembly line job that is embarrassingly parallel with minimal communication overhead may well be better served to have shorter shifts and more workers.

Total net productivity per worker, discounting for any increases in errors and negative side effects, continues increasing well past 40 hours per week. There are a great many tasks where inefficiency grows significantly with additional workers involved; the Mythical Man Month problem is real. In cases like these, you are better off with a smaller team of harder working people, even if their productivity-per-hour is somewhat lower.

This is critical: it isn’t necessary to maintain performance on an extended shift to still contribute value. Productivity per hour can deteriorate, even precipitously, and still be non-negative. Only when you are so broken down that even when you come back the following day your productivity per hour is significantly impaired, do you open up the possibility of actually reducing your net output.

There are cases where the consequences of an increased error rate can be a dominant factor -- airline pilots and nuclear plant operators come to mind. I had to work under FAA mandated crew rest guidelines while operating the Armadillo Aerospace rockets, and I made no complaints.

I believe most research that people glance at and see “declines in productivity with longer hours” are talking about declines in productivity-per-hour, and people jump to the incorrect conclusion that you can get just as much done in less time.

You called my post “so wrong, and so potentially destructive”, which leads me to believe that you hold an ideological position that the world would be better if people didn’t work as long. I don’t actually have a particularly strong position there; my point is purely about the effective output of an individual. If we were fighting an existential threat, say an asteroid that would hit the earth in a year, would you really tell everyone involved in the project that they should go home after 35 hours a week, because they are harming the project if they work longer?