> You need to use a one way policy ratchet to ratchet down the hours per week worked as productivity has increased, otherwise workers will never see productivity gains and society will be stuck on the 40 hour labor work week forever.

The feasibility of this (in the US) is strongly dependent on health insurance not being tied to having a full-time job (often defined as just under 40 hours a week).

Plenty of employers have demonstrated that they can be organized to use mostly part-time labor, but their incentive to do this has been avoiding the obligation and expense of contributing to health insurance and other benefits, rather than giving employees a productivity dividend.