Ryan Mandy, Watson Verity, Entwistle Vikki
Health Economics Research Unit, Institute of Applied Health Sciences, University of Aberdeen, Foresterhill, Aberdeen, UK.
Health Econ. 2009 Mar;18(3):321-36. doi: 10.1002/hec.1369.
Stated preference methods assume respondents' preferences are consistent with utility theory, but many empirical studies report evidence of preferences that violate utility theory. This evidence is often derived from quantitative tests that occur naturally within, or are added to, stated preference tasks. In this study, we use qualitative methods to explore three axioms of utility theory: completeness, monotonicity, and continuity. We take a novel approach, adopting a 'think aloud' technique to identify violations of the axioms of utility theory and to consider how well the quantitative tests incorporated within a discrete choice experiment are able to detect these. Results indicate that quantitative tests classify respondents as being 'irrational' when qualitative statements would indicate they are 'rational'. In particular, 'non-monotonic' responses can often be explained by respondents inferring additional information beyond what is presented in the task, and individuals who appear to adopt non-compensatory decision-making strategies do so because they rate particular attributes very highly (they are not attempting to simplify the task). The results also provide evidence of 'cost-based responses': respondents assumed tests with higher costs would be of higher quality. The value of including in-depth qualitative validation techniques in the development of stated preference tasks is shown.
陈述偏好方法假定受访者的偏好与效用理论一致，但许多实证研究报告了违背效用理论的偏好证据。这些证据通常来自于在陈述偏好任务中自然出现或添加到其中的定量测试。在本研究中，我们使用定性方法来探究效用理论的三个公理：完备性、单调性和连续性。我们采用了一种新颖的方法，运用“出声思考”技术来识别对效用理论公理的违背，并考虑离散选择实验中纳入的定量测试能够在多大程度上检测到这些违背情况。结果表明，当定性陈述表明受访者“理性”时，定量测试却将他们归类为“非理性”。特别是，“非单调”反应通常可以解释为受访者推断出了任务中未呈现的额外信息，而那些似乎采用非补偿性决策策略的个体之所以这样做，是因为他们对特定属性的评价非常高（他们并非试图简化任务）。结果还提供了“基于成本的反应”的证据：受访者认为成本更高的测试质量也更高。研究展示了在陈述偏好任务的开发中纳入深入定性验证技术的价值。
