36 hours is the standard in my country- it's called progress. A century ago it was probably 80 hours for everyone over 12 lol.
However, the free market dictates that you will be outcompeted by anyone who is willing to work 40+ hours. So much for progress.
While it's hard to increase productivity by 25%, it's not a problem for workers to drop productivity by 20%. Owners can work as much as they want, of course.