Reducing the 8 hour work day to fewer hours might be more productive still. But not if that entices more people to get second or third jobs to make bills.
3 x 6 plus one day off, repeat. That's 31.5 hours a 'week' doing away with the archaic week concept. It will never fly, but to me sounds most productive. I find I can't concentrate anymore after 6 hours, no matter how fun it is. At work the extra 2 hours usually result in water cooler talk, unnecessary meetings and email and browsing the internet. Then you go on to crunch for a couple more hours, introducing more bugs along the way... A fresh mind does wonders. I always felt like a zombie coming home after a 10+ hour crunch day. The standard 8-9 hours already took a lot get 'out' of.