"Nowadays we know that total productivity is higher if you have 8 hour work days,"
We know? Surely on a planet with 7 billion people, some of them can maintain their work efficiency for more than 8 hours. What about the Steve Jobs and John Carmack's of the world? I don't see them being 9-5 people.
As a Lyft driver, I am more productive the more hours I work (I top out at 12 hours which I only do on weekends). So the 8 hour rule doesn't apply for everyone.
I think your thesis holds, but I don't think it's clear that your example does (though it certainly still could). Depending on just how much chance of accident goes up over time, and just how great a "productivity" hit we apply for an accident, it is absolutely the case that your productivity falls at some point and it's conceivably the case that it's before 12 (or even 8) hours - though for all I know it's at 15.
I'm sure the fatigue that sets in after (say) 15 hours would be a serious factor in accident risk. I mean truckers are required to stay under a certain work day/week and get enough sleep for safety reasons. Sure if they drove 24 hours straight they would get there faster and in theory be more productive but there are serious safety concerns both with the driver and with the truck (less time for maintenance or inspection)
agreed. My typical pattern on weekend nights is to sleep for 10 hours (yes 10 hours), do what I need to during the day for about two hours, and then get on the road, I'm usually taking anywhere from 1-2 hours of break doing other things that involve momevent (e.g. exercise, social dancing) within that 12 hours, as well, depending on availability.
During the week (when i work more protracted hours) I'm sleeping about 8 hours at least, and I'm also not beholden to an alarm, so I get as much sleep as my body needs. I think I'm probably one of the most well rested people I know, despite pulling twelve hour 'shifts' three days a week.
Obviously I'm more tired after I do the 12 hour shifts than during the week, but I haven't felt so tired that I was at risk of falling asleep on the road (which happened from time to time when I was in grad school).
Yes, also relevant might be the difference between what is safe as a one-off (maybe you really can drive 20 hours safely in a day, if you're well rested beforehand) and what you can do sustainably day after day.
In principle, this is stuff that insurance companies should be on top of...
That seems to have a peculiar and unlikely assumption that they would have produced less by working fewer hours, while almost all human experiences show those at the top of their profession rarely if ever got there by merely punching a timeclock more than the next tier down.
I will never be a world class ballet dancer or world class basketball player simply by putting in a little more time than the next guy.
Plus, in certain fields, even if you are experiencing diminishing returns, you can still squeeze more value out of those additional hours than someone else can.
Imagine one Friday your company calls the law firm you have on retainer. The guy handling your case has already put in 50 hours this week and is only operating at 80% capacity. You are still going to get better work out of him than his coworker, because your guy has everything about your case stored in his head without reading any notes.
On the other hand, if someone was on some type of monitoring duty, where usually nothing happens but if something does happen it's very important that he make the right call (ie guard duty, nuclear power plant operator) I would want to split his work over many people.
Sometimes two 30-hour workers perform better than one 60-hour worker, and sometimes they perform worse.
If Steve Jobs would have worked less, he may not have been removed from the Apple Board. If he had spent more time with his family, maybe the Lisa wouldn't have had the connotations that it had.
These are not conclusive, but they do point us in a direction.
We know? Surely on a planet with 7 billion people, some of them can maintain their work efficiency for more than 8 hours. What about the Steve Jobs and John Carmack's of the world? I don't see them being 9-5 people.