When you're recommending specific radical reform, it helps your argument to analyse specific implementation of said reform, rather than merely extrapolating from a cool research article and sprinkling a few historical anecdotes.
I can't believe that people can get as much done in 4 hours as they can in 8 hours.
Less output == less revenues == ultimately less pay. You can't change math, companies aren't going to get paid the same amount for making less stuff or providing less services.
Maybe the difference is only 30-40% less instead of 50%, but I think most people are willing to put in the extra 4 hours for the additional benefits.
Where is the math that working for 4 hours produces less output than working for 8 hours?
Also, like I said before I don't believe that less output == less revenue. Like I said, I have seen no correlation at all between working more number of hours, or producing more output and revenue. What I have seen though is a strong correlation between working on the right problems and revenue.
You are free to believe what you want. Similarly, I am free to believe what I want based on my experience. As a result, I work for companies that don't have a culture where they believe that output is always directly proportional to number of hours spent. A company that believes working for 8 hours leads to more productivity and I may not be a good fit for each other.
During my career, I have worked for a few small as well as big companies where the management indeed encouraged limiting the working hours to about 4 to 6 per day. All of them had 40 hour week on the contract or legal agreement but the company culture went beyond the written contract to support something like a 25 hour week.
In my career, I did not see any kind of correlation between financial success of the company, productivity and the number of working hours. Financial success had a strong correlation with good decisions made by higher management. Productivity had a strong correlation with high skill-level of engineers and managers hired.
Another way to describe what I mean is: When I worked for one of these companies that encouraged four-hour working day, there were competitors who worked the regular eight-hour working days and were beating us in the competition, and there were also competitors who worked the regular eight-hour working days and were losing to us in the competition.