Behavioral Biases in Stated Preference Valuation of Mortality Risk Reductions: Cost Vector, Anchoring, and Scope Effects

This study investigates how behavioral biases influence stated preference valuation of mortality risk reductions, commonly summarized as the value of a statistical life (VSL). Using a discrete choice experiment (DCE) combined with a contingent valuation double-bounded dichotomous choice and an open-ended follow-up, we elicit individuals’ willingness to pay (WTP) for cardiovascular mortality risk reductions. In a randomized design, we varied the cost attribute across three cost range treatments and manipulated information disclosure and feedback to examine three behavioral phenomena: cost vector effects (whether the range of costs presented affects WTP), scope insensitivity (whether WTP scales appropriately with the magnitude of the risk reduction), and anchoring (whether initial cost cues affect subsequent responses). Our results show that mean VSL estimates can vary by up to ~25% between cost treatments. Furthermore, WTP responses exhibit partial scope insensitivity – larger risk reductions do not proportionally increase WTP – indicating a deviation from theoretical expectations. Importantly, we find no strong evidence of anchoring: neither revealing all attribute levels upfront, nor starting with extreme cost levels, nor providing feedback on quiz questions significantly affected respondents’ choices or WTP. Our findings underscore the need for careful survey design. Even if VSL distributions remain statistically similar across cost frames, substantial shifts in mean magnitudes could be consequential for policy. We call for standardized guidelines on cost attribute selection and survey protocols to mitigate bias, ensuring that stated preference methods yield reliable welfare estimates for health policy decisions.