A Systematic Review of Elicitation Methods for Distributional Preferences in Healthcare Regarding the Concentration and Dispersion of Health Benefits

OBJECTIVES: In conventional quality-adjusted life-year maximization, each unit of health is valued equally. It overlooks distributional preferences, such as whether health improvements should be concentrated on a smaller number of individuals or dispersed across a larger population. It is plausible that these preferences follow an S-shaped pattern, in which marginal social value of health gains initially increases before diminishing after a threshold. This review aims to identify and evaluate the methods used in empirical studies to elicit S-shaped preferences. METHODS: Searches were conducted in PubMed, PsycINFO, and EconLit in August 2024 and October 2025, with 1 round of citation chasing for 4 key articles. Studies were included if they elicited preferences on concentration and dispersion of health gains among otherwise identical individuals. Data synthesis was conducted narratively. RESULTS: Thirteen studies published between 1994 and 2025 were included, collectively involving 6799 participants. All studies used a Person Trade-Off (PTO) approach, but 2 also used Time Trade-off. Five key methodological themes emerged: whether health gains should be measured in life-years or health-related quality of life, the threshold between concentration and dispersion, perspective, framing effects, and specification of the social welfare functions. CONCLUSIONS: This review highlights methodological challenges associated with eliciting preferences for concentration and dispersion. Although there is a consensus on the use of PTO, other heterogeneity such as pool size or perspective and sparse evidence on the threshold effect warrants further research.