Since 1950 the retirement duration only grew by 50% (the life expectancy at 60 went from 77 years to 84 [1]) can you recall how much the productivity grew from that time ? If we cannot afford to pay 50% more when productivity grew by a factor 3[2], there is indeed a problem of repartition.
The relevant growth % is the total number of life-years being funded by retirement.
Since the total populaton of US in 1950 was 150, and is 300 million today -- assuming equal distribution of ages -- that's a 4x increase in life-years to fund.
ie., 2x for population size, and 2x for length of retirement
And worse, the distribution isnt equal, ie., there are more of the population today in retirement than in 1950.
So it's at least 4x the number of years, and probably closer to 6x.
No need to take the population into account because I used the per capita productivity.
And do you have figures for the doubling of the retirement duration ? As I showed above, it only increased by 50% in England and I'd be surprised is the American raise was higher since life expectancy is lower there (in part due to a less efficient health system).
Well it's a rather difficult calculation to make in this fashion.
The relevant data needed is total number of retirement hours funded, total productive output, and total "other" essential spending.
What's also happening is the cost of healthcare is increasing, quite dramatically, and eating up productivity gains.
I have a strong suspicion that we're way ahead of "general essential" social spending today, compared to 1950s, per-captia; productivity gains included.
[1] https://ourworldindata.org/wp-content/uploads/2013/05/Life-e... https://www.ons.gov.uk/employmentandlabourmarket/peopleinwor...