Willingness-to-pay and demand curves: a comparison of results obtained using different elicitation formats.

Health economists use "willingness-to-pay" to assess the prospective value of novel interventions. The technique remains controversial, not least with respect to the formats under which values are elicited. The paper analyses the results of a series of studies of the same intervention valued by the same population, in which different elicitation formats were employed. The findings support the hypothesis that data collected using different formats give rise to different demand curves, from which different inferences about demand elasticity, profitability and consumer surplus will be derived. Judgements as to the relative merits of rival interventions depend crucially upon whichever format has been used to evaluate each intervention.