Anecdotally, we introduced a 25 hours (5 days, 5 hours per day) work week at full pay in our company (digital services, creative) and maintained it for several years and observed a reduction of productivity (in terms of output) of 10-20% compared to the reduction of working hours of 37.5%. We also saw much higher employee satisfaction and self-reported mental health improvements. Most of the employees were women so the reduction in working hours also often translated to a significant relative increase in leisure time as much of their non-working hours was otherwise taken up by family, care work and chores (which isn't to say their partners were slobs but gendered expectations still exist in our society and it's not just the men reinforcing them).<p>Our biggest problem was that this was difficult to roll out to all people working for the company. E.g. you can't really cut the hours for cleaners coming in for a few hours per week because their hours are mostly defined by their workload and a 37.5% reduction across the board also means someone who previously did 20 hours would now do 12.5 hours, which translates to a much greater loss of productivity if spread out across more than two days. The founders also pretty much kept working full time as before.<p>The reduced number of working hours also really put the spotlight on people who were already struggling with productivity before, which one might argue is a good thing. Also for legal reasons the contracts remained unaffected as this was an open-ended experiment, not a legally binding benefit. The employees were also interviewed before and during the process and most were initially opposed to the idea because they feared they wouldn't be able to handle their workloads in less time.<p>It's worth mentioning that just like WFH policies, this is something that simply doesn't work for everyone. If you have a factory with a fixed output over time and productivity of an employee is tied to time at the machine, productivity loss will translate 1-to-1 from reduced working hours. Likewise in retail working hours are dictated by opening hours. You can still reduce working hours by introducing/adding shifts of course but there is no economic incentive for companies to keep paying employees the same for fewer hours in these jobs unless coerced to do so through collective bargaining. Remember that while many credit Henry Ford with popularizing the 40 hour work week and he did provide many rationalizations for it at his own company, the 40 hour work week only became law (along with many other improvements of working conditions) after massive protests from unionists and anarchists, including the Haymarket massacre[0]. It wasn't simply handed to workers, and certainly not voluntarily.<p>[0]: In case you're unfamiliar with the term, the Haymarket massacre or "Haymarket affair" refers to an incident where police shot and killed an unknown number of unarmed protestors and striking workers following an explosion that killed seven police officers and at least four workers. Eight people were charged and sentenced (seven being sentenced to death) for the bombing, though it's not clear if any of them were actually involved in the bombing itself or its planning. The police officers who had shot and killed protestors never suffered any consequences.