Perhaps nothing, the major way health insurance is required today is by number of hours (30 per week). To avoid this cost companies reduce hours. Overtime hour

Perhaps nothing, the major way health insurance is required today is by number of hours (30 per week). To avoid this cost companies reduce hours. Overtime hours apply only to hourly and non-exempt employees today and only for hours over 40. Thus a change to the work week might start with a cap on salaried employees hours and required overtime for hours over 40. With fewer exceptions would a 4 day work week might result from working 4 10's first. If overtime is set at 32 hours as well this would push down hours per day. I can't foresee a cap on hours per day so this could be instituted by companies requiring 4 days in office. If the U.S. with a mine to universal healthcare I'm worried the wage decline would happen naturally anyway. However that may lead to more flexibility in hours with companies opting to allow more control over number of hours as extra costs more scale more slowly