Pensions are inherently unsustainable because they guarantee returns. What investor in the world is ever able to guarantee returns, especially at the volume of clients that get served by pensions? It is likelier that the pension:
The cash payout part of a pension is, as you point out, just math. The problem is health care. If you retired in, say, 1980 with a pension that included health care, the company ended up paying out (on average) far, far more than they expected.
That is a fair point. I don't know how to handle healthcare because it is a good with almost infinite demand (who doesn't want to live longer or be healthier), and a finite supply (of doctors, nurses and other folks who can provide services to help us live longer healthier lives). What happens when you have demand with limited supply?
- gets rid of the obligation by selling it to someone else: https://www.forbes.com/sites/joannmuller/2012/06/01/gm-unloa...
- raises more capital or debt to fund the pension (or in the case of government pensions, raise taxes) and kick the can down the road: https://www.wsj.com/articles/gm-to-take-on-3-billion-in-debt...
- just lets bankruptcy kill the obligation: https://mobile.nytimes.com/2006/10/24/business/retirement/24...