RTI Health Solutions, Research Triangle Park, NC, USA.
Health Econ. 2011 Mar;20(3):323-30. doi: 10.1002/hec.1591.
Willingness-to-pay (WTP) estimates derived from discrete-choice experiments (DCEs) generally assume that the marginal utility of income is constant. This assumption is consistent with theoretical expectations when costs are a small fraction of total income. We analyze the results of five DCEs that allow direct tests of this assumption. Tests indicate that marginal utility often violates theoretical expectations. We suggest that this result is an artifact of a cognitive heuristic that recodes cost levels from a numerical scale to qualitative categories. Instead of evaluating nominal costs in the context of a budget constraint, subjects may recode costs into categories such as 'low', 'medium', and 'high' and choose as if the differences between categories were equal. This simplifies the choice task, but undermines the validity of WTP estimates as welfare measures. Recoding may be a common heuristic in health-care applications when insurance coverage distorts subjects' perception of the nominal costs presented in the DCE instrument. Recoding may also distort estimates of marginal rates of substitution for other attributes with numeric levels. Incorporating 'cheap talk' or graphic representation of attribute levels may encourage subjects to be more attentive to absolute attribute levels.
意愿支付 (WTP) 估计值源自离散选择实验 (DCE)，通常假定收入的边际效用是恒定的。当成本在总收入中占很小的比例时，这一假设与理论预期是一致的。我们分析了五个 DCE 的结果，这些结果允许对这一假设进行直接检验。检验表明，边际效用经常违反理论预期。我们认为，这一结果是一种认知启发式的人为产物，这种启发式将成本水平从数字刻度重新编码为定性类别。受试者可能不会在预算约束的背景下评估名义成本，而是将成本重新编码为“低”、“中”和“高”等类别，并进行选择，好像类别之间的差异是相等的。这简化了选择任务，但破坏了 WTP 估计值作为福利衡量标准的有效性。在医疗保险覆盖扭曲了受试者对 DCE 工具中呈现的名义成本的感知的情况下，重新编码可能是医疗保健应用中的一种常见启发式。重新编码还可能扭曲对具有数字水平的其他属性的边际替代率的估计。纳入“廉价谈话”或属性水平的图形表示可能会鼓励受试者更加关注绝对属性水平。
