Health inequality aversion across multiple equity dimensions: a benefit trade-off experiment in South Korea

As health technology assessment increasingly incorporates equity concerns, inequality aversion parameter (IAP) estimates are needed for equity-informative economic evaluation. We conducted an online benefit trade-off experiment in 2025 (n = 3000) to elicit IAPs for South Korea by comparing health-based and income-based framings under identical scenarios, and by examining region-based inequality using different outcome measures. In the first set, healthy life years (HLYs) were used as the outcome, while groups were defined by either health level or income. In the second set, region-based inequality was framed in terms of either final health outcomes, measured as HLYs, or access to emergency room (ER) care. Atkinson and Kolm-Pollak parameters and equity weights were estimated, alongside the proportion of respondents with inequality aversion. Multiple regression examined sociodemographic factors associated with inequality aversion. In an analytic sample of 2612 respondents, approximately 80% were willing to forgo some aggregate health gains to reduce inequality in both the health-based and income-based tasks. The median Atkinson parameter was 16.0 for the health-based task and 7.93 for the income-based task, with corresponding equity weights of 6.24 and 2.48, although the difference was not significant. In the region-based tasks, inequality aversion was more prevalent when inequality was framed in terms of ER access than HLYs (81.3% vs. 70.9%). Lower-income and non-metropolitan respondents did not express stronger aversion to income- or region-related inequalities. These findings suggest that public preferences over health inequality depend not only on which groups are worse off, but also on how disadvantage is framed and interpreted.