40 hours isn't done by custom, it's done because it's proven to be the most productive working week. This isn't a case of scientists discovering that "what peop

40 hours isn't done by custom, it's done because it's proven to be the most productive working week. This isn't a case of scientists discovering that "what people are used to is what they're most productive at". For most of the industrial revolution people worked 12hr+ days, and that was considered, even by the labour force, to be perfectly acceptable. Hauling that back to 8 hour days was a herculean task that no major factory owner was going to do without damn good evidence that it would improve things. That's a relatively biased misreading of the history of the 8 hour day. You're implying that science and factory owners decided on it. Yet the labor movement, industrial action and strife played an outsized role. The 8 hour day movement is an old one (http://www.pbs.org/livelyhood/workday/weekend/8hourday.html http://www.pbs.org/livelyhood/workday/weekend/8hourday.html), and the call for 8 hours was echoed by the labor movement for decades after.