No they have not. Studies by motivated parties show in some cases there are diminishing returns.

It's a non-sensical argument. If a 4 day work week is more productive than a 5 day work week it means the 5th days is producing negative work. You could literally do nothing every Friday and you would not be less productive than a 4 day work week.

> It's a non-sensical argument.

Your take is equally non-sensical. There is no magical constant unit of time that represents maximum productivity. It’s all relative and fluid. It’s based on many many variables. And even if such a time existed for one person in one company for one week, it wouldn’t be neatly packaged like “40 hours”. It would likely seem random like 34 hours 20 minutes and 25 seconds.

Arguing over such a universal time is as much a waste a time as arguing over the perfect diet. It’s relative.

What's nonsensical is your bad take. First and foremost, if workers say they're happier, you have no method of disputing that and every study that captures the employees perspective is literally saying the exact same thing. Find me some data that says humans want to work longer hours, we will all wait...

It also sounds like you're not familiar with simple ideas like Parkinson’s Law. Listen to yourself, you don't think people are fucking off at work? It's business hours and you're on hacker news not doing work, case and point.

> You could literally do nothing every Friday and you would not be less productive than a 4 day work week.

This would be an accurate statement for most work places. People are often creating negative value in the modern workplace in the form on tech debt, new bugs, unwanted features, meetings that drain the rest of the staff...

5 days isn't productive for knowledge and creative work, it leaves people in a state of perpetual burn out and greatly lowers the quality of output.

That's not non-sensical at all. It's completely plausible. In any task, fatigue results in diminishing marginal productivity, to the point where taking time to rest and recover will sometimes boost total productivity more than spending that time working. Evidence, not blanket dismissal, is required to determine if that's true for Fridays.

> If a 4 day work week is more productive than a 5 day work week it means the 5th days is producing negative work

Or it could mean that increasing weekly time off by 50% improves people's happiness and productivity, or that a 5 day work week results in days of work that are less productive than in a 4 day work week.

Productivity is output per hour worked. So you can work fewer hours and be more productive and produce less output all at the same time.

There's reason for skepticism, but negative work doesn't seem impossible to me. If you've got a 2 hour status meeting that zaps your motivation, reducing productivity by 50% for the remaining 6 hours of the day, that meeting produced -1 hours of work. (And if you postulate that 32 hours is the limit of productivity for the average employee, those kind of soul-sucking meetings are exactly what you'd expect to be scheduled to fill out the remaining 8.)

It’s very easy to produce negative work as a programmer so this isn’t as silly as you assume. How often have I spent hours debugging some code only to realize I did something stupid after staying up late the previous night.

If that were true, why isn't every company adopting 4 day work weeks?

How many have even tried it? Companies are profit-seeking but that doesn't mean they will automatically make correct profitable decisions at every juncture. They're led by humans who generally make small conservative changes based on intuition. We see companies languish, stagnate, and miss critical strategic opportunities all the time.

Poor management is endemic. Managers are for the most part trying to maximize their ego/status. This means having their "underlings" grinding away (preferably in view) for as many hours as possible. That this situation is bad for the company doesn't matter since management is the one executing the poor decisions.

I think there is a change of attitude with a shorter work week. If I am working 9-5 at the same place everyday, I basically live there. It is easier to decide to take more breaks because there is no Friday to relax or get chores done or go to appointments. I take every other Friday off and it helps me focus more at work. I schedule all my weekday appointments for Friday (as much as I can). Monday thru Thursday I can push a little harder and be a little more focused because I know I have Friday (or a week from Friday) to take my dog to the vet, me to the doctor, or whatever else I need to do. I would love a real 4 day work week.

Power, greed? Why do CEO's make 100x their employees? Some things just don't make sense.