Correct representation is extremely difficult for a variety of reasons:
- Many real problems do not only have multiple types of customers (or decision-makers), but are also confronted with multiple stages;
- People have widely varying value system; also, one cannot know for sure what one wil think in say 10 years;
- Future generations are even more difficult to take into account (the Delphi technique may help somewhat). This is a strong argument against the idea of a marketplace for decision making. 

 In order to achieve a reasonable approximation, the method of explicit assumption making is applied. Comparing utilities remains a problem, nevertheless.