Why did Keynes believe that, say, a doubling of efficiency (through technology) would half work time for everyone? Sure it’s a solution to the equation, but so is what actually happened[1]: half the workforce gets laid off. This halves the costs, which facilitates price reduction and thus a competitive edge. Did Keynes believe that benevolence would win over profit? Don’t get me wrong, I wish it had, but that seems a…
Technological progress has made labor productivity itself a lot more uneven and sharply unequal than it used to be when Keynes was writing. So the currently most marginal workers tend to be laid off first, especially given the increasing regulatory barriers that have made low-productivity positions unsustainable since then.