If we are talking about modern people only working 2 days a week and still being as productive as people were in the past while working a whole week, then you h

If we are talking about modern people only working 2 days a week and still being as productive as people were in the past while working a whole week, then you have to see that 3.5 times the population increases the number of people able to do work. So either the work is divided among more people and people work even less and are able to live, or the bosses keep all the cash and make people work a full week and give them a marginal percent of what they brought in and everyone is worse off.