OBJECTIVES: In most stated preference studies in health economics the valuation of health states has reflected individual (“selfish”) preferences only. Social willingness-to-pay (WTP), i.e., WTP an extra in public tax or mandatory health insurance premiums in exchange for access to a health care intervention, should allow to also capture option value and caring externalities. We designed a Discrete Choice Experiment (DCE) to explore social preferences of citizens in Switzerland with regard to coverage decisions by mandatory health insurance, with particular attention to the potential role of rarity.

METHODS: Based on a literature review, a Swiss multi-stakeholder consensus (“SwissHTA”), and an international expert consensus, we identified severity, health gain, age, and prevalence as relevant attributes of health care interventions, using additional health insurance premiums as cost attribute. Following pretests, the survey enrolled 1,501 respondents, who had participated in an initial preference formation phase. We assessed the relative importance of the attributes and – by randomization into subgroups – the impact on choices by the level of information on “rarity” and cost per patient (framing effects). The study further included a utility comparator.

RESULTS: We find empirical support for the importance of all attributes tested, with health gains (changes in life expectancy and quality of life) and incremental cost (from a citizens’ perspective) being more relevant than prevalence and the age effect observed in the experiment. Despite decreasing social WTP with decreasing prevalence, our data point to a profound increase of implied WTP per case with decreasing prevalence.

CONCLUSIONS: Results suggest that all attributes tested contribute to the social valuation of health interventions, in contrast to the assumptions underlying the conventional logic of cost effectiveness – indicating potentially far-reaching implications for the use of economic evaluation in the context of HTAs. We will discuss limitations of the study and future research needs.