These values are appropriate costs and benefits. The challenge lies in measuring these values in meaningful scientific ways, that is, ways that can be validated and replicated. In general, because there are no behavioral footprints from which to infer value survey based approaches are used to derive indirect values. Typically, these analyses present detailed scenarios to respondents that include information about the program under consideration, what it hopes to accomplish, how it will be paid for, and over what time period actions will take place. Various formats are then employed to obtain a contingent value that is an estimator of actual willingness to pay.
Some analysts use a family of approaches termed conjoint analysis to seek similar information.
These are termed stated preference measures because respondents are asked to state their willingness to pay. Stated preference measures have been criticized for a large number of reasons, some quite esoteric and others quite practical. Some question, for example, if individuals actually have preferences for a diverse and nearly limitless set of resources that can be estimated in this way. Others question the sensitivity to the quality of the program being purchased. Still others concern themselves, that respondents, sensing that their answers may affect policy, respond strategically with very large or with zero responses.