It's an major confounding factor in all productivity studies, and IMO underappreciated because UI researchers generally don't want to get involved in politics.

It's an major confounding factor in all productivity studies, and IMO underappreciated because UI researchers generally don't want to get involved in politics. Social status depends more on relative wealth than absolute wealth. When the owning class takes approximately 100% of the generated wealth from improvements, the direct effects of improved productivity only hurt the worker. (They gain indirectly, because improved productivity helps society as a whole, but the marginal gain to the worker from any individual improvement is always small, so there's a tragedy of the commons here and the incentive is always to resist improvements.)