In today's business world, it's almost universally assumed that you can boost corporate productivity by encouraging and expecting your salaried employees to work as many hours as possible per day.

Research says otherwise. Long work hours create stress, and stressed employees get sick more often, make expensive mistakes, become increasingly discouraged, and eventually leave.

Unfortunately, despite all the evidence that our "cult of overwork" is both ineffective and destructive, few executives are brave enough to buck the conventional wisdom. Not so at Perpetual Guardian, a New Zealand-based financial services firm.

As an experiment, the CEO told employees, who normally worked 40 hours a week, to work only 32 hours, with no cut in their pay.

According to conventional wisdom, cutting the work hours should have resulted in a net decrease in productivity, in the sense that the company would be paying the same amount of money for less work getting done.

In fact, the opposite occurred. The employees experienced a sharp increase (24 percent) in work-life balance and, as a result, were more effective. According to professor Jarrod Haar of Aukland University of Technology, as quoted in the New York Times:

"Supervisors said staff were more creative, their attendance was better, they were on time, and they didn't leave early or take long breaks. Their actual job performance didn't change when doing it over four days instead of five."

Think about that for a second. People were getting just as much work done while spending 80 percent as much elapsed time at doing it. Sound too good to be true? Well, it turns out that the surprising result is exactly what you'd expect, if you're familiar with current research. 

For example, according to a 2016 survey of nearly 2,000 U.K.-based office workers, the average worker only accomplishes 3 hours of work each day (a little less actually), regardless of how many hours they physically spend at the office.

What happens to the rest of the time? Exactly what you'd expect. In addition to those three hours of actual work, employees check social media, Web-surf, discuss non-work activities, make and consume food and drinks, send texts, make personal calls, and so forth.

Oh, and one more thing. Employees spend some of that at-work-but-not-really-working time looking for another job, probably because they realize they're wasting a huge chunk of their time hanging out at the office for appearance's sake.

Now, you might think that the "solution" to this "problem" would be to hold the employees' feet to the fire so that they do more actual work and less messing around. You'd think wrong, though, because the human brain is not set up to focus for hours at a time.

According to research cited in  Business Insider, most people can concentrate on one thing for "about 20 minutes at a time" and many people--especially in open plan offices--"struggle to stay on task for more than 10 seconds."

In other words, if you think that working long hours is crucial to your success--or that of your employees--you're kidding yourself. It's all about working smart, not working long. But you knew that already, right? The real question: Are you brave enough to do something about it?