Decision makers need to make their own value judgements of the significance of risks . . . All three, benefits, costs, risks can be quantified, with the results and implications understood by the public at large. There are few serious challenges to the need to discount cost streams. If for no other reason than the alternative of not doing so gives outlandish answers. I have seen discounting not used on large program estimates in the public sector with some very predictable and extremely undesirable results.
Benefits are tougher than costs, but manageable.
The move toward converting benefits to imputed income streams is relatively recent. While I have explored it some, follow attempts now, and look forward to any breakthroughs, imputed income from benefits looks like a black hole to me. Imputed monetary benefits and subsequent discounting offer far less than discounting cost streams for at least three reasons. Imputing income from benefit streams is contentious. It requires extensive intervening assumptions and complex calculations between the physical, plain-language benefits and imputed income.