It's precisely what Keynes meant. He meant that 15 hours of labor now will buy you what 40 would then. How could he have meant anything else?
How would he anticipate houses 50% larger than his generation's, or cars with twice the horsepower at four times the gas mileage, or universal air conditioning (as few houses in the US lack air conditioning now as lacked running water in 1950) or a monthly bill for Internet or proles being able to afford intercontinental flights more than once in a lifetime?
He postulated eightfold increse in economy, though not clear at what working hours. If he assumed 40 hours then and eightfold productivity increse, with 15 hours that would still be threefold increase in living standards. The productivity has increased even more than eightfold.
Keynes was quite damn good at anticipating things.
Yes. That's math, the rule of 72. At a 2% growth rate the economy will be 8 times larger in 108 years, more or less. The rate is a bit higher, so we're a bit over 8 in the 95 years since that's been written.
> Keynes was quite damn good at anticipating things.
But that's not anticipating things, that's projecting an existing growth rate out for another century. Improbable really that it would neither rise nor fall, and one of the reasons it hasn't fallen is that we didn't cut our work week to 15 hours. So the only thing (in this context) that he really anticipated was wrong.
How would he anticipate houses 50% larger than his generation's, or cars with twice the horsepower at four times the gas mileage, or universal air conditioning (as few houses in the US lack air conditioning now as lacked running water in 1950) or a monthly bill for Internet or proles being able to afford intercontinental flights more than once in a lifetime?