This is also a curious method for opening more employment and reducing potential income inequality. If a factory needs to produce X things, and each worker produces Y things per hour you will always need X/Y working hours. If workers reduce working hours by 20% then you'll need to hire 20% more workers or improve Y (productivity) by 20%.

If the majority of the economy follows a linear production curve in hours worked, then this opens many jobs. Not a bad deal for a mature economy like JP, but will be interesting to see what un-forseen dynamics emerge.