Construction costs are currently skyrocketing

Pensions must always be taken from current income, where else?

There is, however, a difference. The pay-as-you-go pension system based on wages and salaries, as we have it now, can only draw its benefits from wages and salaries in Germany. This poses multiple problems: Firstly, demographics are worsening; instead of 2 or 3 workers per retiree, the ratio will soon be reversed. Secondly, it relates only to labor, but there are other factors of production. Currently, automation, i.e., capital, is especially important. Thirdly, the levy is imposed on all labor, regardless of whether the respective company is on the brink of bankruptcy or is generating record profits.

A funded system also allows other factors to be tapped very easily. Capital gains are primarily generated in profitable sectors. Capital gains can also be generated outside Germany. In the economy of industrialized countries, capital is the dominant factor. However, we still conduct social policy as if labor dominated decades ago, partly due to favorable demographics. Of course, this could now be managed through tax subsidies, but the problem is that in practice taxes are easiest to collect from the middle class and hardest from international corporations. However, capital gains can very easily be collected from these via the stock market.

It is not an either-or, but a both-and. Some countries realized this ages ago and stabilized old-age provision on multiple pillars in the form of a statutory pay-as-you-go pension and funded capital in the form of private provisions and occupational pensions. Here in Germany, there is no courage to demand serious private provision from people and to give them the necessary freedom to do so. Here, private provision has rather been seen as short-time work for insurance agents, and in the end, you get 50€ Riester pensions.

And every retiree then purposefully depletes their capital to zero by death excluding funeral costs? How? And: Why?

No, they can already blow it up beforehand (and then live off the basic pension) or inherit it. That is possible now too, a retiree can spend or save and inherit their pension. In fact, this even preserves more demand, since a prematurely deceased person who receives less than their contribution payments as a payout would, in my model, continue to inherit the remaining capital stock instead of it just resulting in fewer payouts. So my model would even be demand-stimulating.

(I call it "my" model without any claim to authorship, it is just easier in the context of this thread).

There is a difference though. The pension based on the pay-as-you-go system on wages and salaries, as we have it now, can only draw its benefits from wages and salaries in Germany. This is a problem in several ways: First, the demographics are worsening, instead of 2 or 3 workers per retiree, the ratio will soon be reversed. And second, it only relates to labor, but there are other factors of production. Currently important is especially automation, i.e., capital. Third, the levy is applied to all labor, regardless of whether the company in question is on the verge of bankruptcy or making record profits.

A funded capital system also very easily allows tapping into the other factors. Capital returns are mainly generated in profitable sectors. Capital returns can also be generated outside Germany. In the economy of industrialized countries, the capital factor dominates. But we are still doing social policy like decades ago when labor dominated, partly due to favorable demographics. Of course, this could now be regulated via tax subsidies, but the problem is that in practice taxes are easiest to collect from the middle class and hardest from international corporations. Capital returns can very easily be collected from these via the stock market.

It is not an either-or but a both-and. Some countries recognized this ages ago and have made old-age provision stable on several pillars in the form of a statutory pay-as-you-go pension and funded capital in the form of private provision and company pensions. Here in Germany, they lack the courage to ask people for serious private provision and to give them the necessary freedom for it. Here private provision was rather seen as a job creation measure for insurance agents and in the end, you get 50€ Riester pension.

You describe the problem completely correctly.

You also name the solution: tapping into capital returns.

So sharing the profits of companies in pensions. This is possible via the stock market but only with companies that also place products there (bonds/shares). Alternative?

The problem I generally pointed out remains: demand for a company’s shares cannot be the same as demand for a company’s products. Only the latter generates the revenues from which pensions must be paid.

It is national accounting: What is saved in total by acquiring the funded pension entitlements must come into the system elsewhere as debt, otherwise it does not work. Who is supposed to take on this debt?

You simply cannot avoid a few “laws of nature” of economics.

(This is not to say that you do not have valid points. There are just often hidden side effects I want to point out).

The pension has already been earned. At least the contributions.
The resulting return in private retirement provision only occurs if corresponding profits have been made (i.e., debts have been taken on and repaid). During retirement and after death, both amounts come back into circulation, so demand is not withdrawn from the market, but only (temporally) shifted and only once. From an overall economic perspective (over time), it does not matter when the demand hits the market.
But I think we have really drifted off course. It hasn’t been this bad for a long time...

Could it be that Pflastersplitt has become much more expensive? I only find offers >100 EUR /t and I think it was significantly below that in the spring?

The catchy phrase "The money is not gone, it just has someone else" highlights the problem of capital-funded retirement provision. If someone wins something, someone else must necessarily lose. Anything else would be uncontrolled growth forever, and that simply cannot exist in a country or on a planet with finite resources. Where does the money come from if I make a 10% return per year with stocks? Those who bought their stocks more expensively than I did pay that price and get left empty-handed when I and others then sell and the price falls...

Where does the money come from if I make a 10% return per year with stocks? Those who bought their stocks more expensive than I did pay that, and end up empty-handed when I and others sell and the price falls...

A bit of an oversimplification. It's a bit more complex. Returns are on the one hand the distributions and secondly only a theoretical value.
Profit is also possible for everyone but only if demand is higher than supply. The price rises and everyone theoretically becomes richer.
On Black Fridays, however, almost everyone jumps off the skyscraper.