Observing the negative interest bonds in Switzerland, Denmark, GErmany the value of higher presently (credit-free) outgoing cash flows seems less important than the value of lower future (credit-free) incoming cash flows, when the time of the flows is chosen. This is also the case for intertemporal rate marginal substitution (eg: pensions), but such a model is used to model a margin rate and not the whole rate.
When using an utility function for example, does it make sense to optimize the portfolio not to maximize prezent value in base currency, but to minimize the error to get future liquidities right in the currencies of interest. Or you do not scale your prices to the base currency at all, but to future number units of a bond, which is the number you try to maximize.
