Willingness to pay and size of health benefit: an integrated model to test for ‘sensitivity to scale’
研究支付意愿是否随健康收益规模增加而上升，提出整合模型同时检验内部和外部敏感性，并应用于减少症状天数的调查数据，发现数据适当转换后支付意愿具有规模敏感性且符合边际效用递减。
A key theoretical prediction concerning willingness to pay is that it is positively correlated with benefit size and is assessed by testing the 'sensitivity to scale (scope)'. 'External' (between-sample) sensitivity tests are usually regarded as less powerful than 'internal' (within-subject) tests. However, the latter may suffer from 'anchoring' effects. This paper studies the statistical power of these tests by questioning the distributional assumption of empirical data. We present an integrated model to capture both internal and external variations, while controlling for sample heterogeneity, applied to data from a survey estimating the value of reducing symptom-days. Results indicate that once data is properly transformed, WTP becomes 'scale sensitive' and consistent with diminishing marginal utility theory.