Well I imagine efficiency is measured by the amount of work done divided by the number of hours worked... I know the salary-man culture in Japan is pretty grueling, so I imagine the hours are super high. And since they're so fucking tired (Japanese men sleeping at the office is a meme), the work suffers.

So they are not only working far more hours than average, but getting the same amount or possibly even less, work complete in that time because of energy levels/morale.

Simple math that you'd hope even a CEO could grasp.