We examine whether subjective wellbeing outcomes can be compared across studies that use two alternative wellbeing metrics: life satisfaction (LS) and the World Health Organization’s WHO-5 index of mental wellbeing. If comparisons are meaningful, it would extend the use of wellbeing years (WELLBYs) to a wide range of health intervention evaluations. Using multiple surveys and multiple econometric approaches, we test whether a linear relationship between LS and WHO-5 holds across the entire range of both variables, including for population sub-groups. Linearity is required for both metrics to act as candidate proxies for utility, a key assumption underlying WELLBYs. Tests indicate that LS and WHO-5 are approximately linearly related except at very low levels of either variable. Considerable noise is, however, present in the relationship. Hence, caution is needed when including very low values of either measure for aggregate analyses (e.g. in constructing WELLBYs) or in using either measure for diagnostic purposes.
Grimes et al. (Tue,) studied this question.