Keynes, who is having a come back these days, was also in favour of a reduced week, based on the assumption that the prosperity societies have would lead to less work.

We can certainly afford it, but if 40 hours is more efficient than 30 hours, in a competitive framework the former will triumph. Of course, theres a reasonable amount of evidence (as I understand it) that beyond short pushes to get stuff done, stretching the working day reduces productivity: this is one of the reasons companies excepted union demands for an 8 hour day.

It is kind of weird that we have a 5 day working week and not a 6 day or 4 day week if you think about it. One suspects that thats a cultural creation rather than an inevitable one.