 More fundamentally, both approaches measure consumers' hypothetical, rather than actual, WTP and
thus can generate hypothetical bias, which the economics literature defines as the bias induced by the hypothetical nature of a task.A direct approach to elicit actual WTP is a mechanism that Becker, DeGroot, and Marschak (1964) propose (Becker–DeGroot–Marschak method), in which a participant is obligated to purchase a product if the price drawn from a lottery is less than or equal to his or her stated WTP.An indirect approach for determining actual WTP is the incentive-aligned choice-based conjoint (ICBC) analysis, in which participants are also obligated to make a purchase based on WTP inferred from their revealed preference, using the BDM mechanism.