The 40 hour week was a compromise for labour regime that doesn't grind people down into a physical wreck. Remember it wasn't office work but production jobs whe

The 40 hour week was a compromise for labour regime that doesn't grind people down into a physical wreck. Remember it wasn't office work but production jobs where your pee breaks were regulated. There hardly was a technological difference with immediate pre- and post-unionization periods. Regulating the workday had the extra effect of labour appreciating in value. One couldn't run factory on two 12-hour shifts anymore, so had to hire for third shift. It pent up the demand for workers, who could command better terms. This certainly helped establishing blue collar middle class.