And on the other hand, in a pay-as-you-go system, as in a lot of European countries, we soon start that expeeiment involuntarily, when all the Boomers finally are retired. It would easily work, when the owners are taxed accordingly. On the whole society level we than have more retirement years than working years.

Not sure. You can tax the owners accordingly but they cannot sustain the cost for everyone else.

Only if the gains in productivity also produce a rise in the salaries

Yep, that is the condition. It was met between 1900-1975. Since then the productivity gains were larger than the salary gains. That is, why it feels wrong to want to work less these days. But it is a political decisison which was driven by greedy owners. They wanted more of the cake and now tell their workers “you cannot work less, even when your output has risen like never before”.

I agree that owners are now more greedy (not last because for the market now the only thing that matter is the next quarter) but as I can see the real problem is that every time we are talking about working less/retiring earlier we ignore the reality: we live longer and longer and with all the gain in productivity we cannot expect to offset the fact that we want to work less years.

I would agree to work 4 days a week with the same pay if the productivity is the same, but if we want to retire earlier and live longer I see no other way that work some more years because what you will get once retired is proportional to what you put aside now (accounting capital gains and everything else), there should be an balancing between the two period duration, especially if we don’t want to have an heavy impact on the social welfare.