The traditional 9–5 workday is poorly structured for high productivity. Perhaps when most work was physical labor, but not in the knowledge working world we now live in.
Although this may be obvious based on people’s mediocre performance, addiction to stimulants, lack of engagement, and the fact that most people hate their jobs — now there’s loads of scientific evidence you can’t ignore.
The most productive countries in the world do not work 8 hours per day. Actually, the most productive countries have the shortest workdays.