The whole pension fund concept only works because it declares how much is going to be paid out.
Who’s going to pay in if the fund expects a guaranteed commitment but refuses to give such in return?
It’s called a defined contribution pension as opposed to a defined benefit pension. They exist.
401ks don’t guarantee results for a given amount of input, and people still stuff away lots into them?
> Who’s going to pay in if the fund expects a guaranteed commitment but refuses to give such in return?
Literally defined contribution [1].
[1] https://en.wikipedia.org/wiki/Defined_contribution_plan