Comparing South Korean and US self-rated health using anchoring vignettes

Purpose: This study compares the self-rated health (SRH) of South Korean and US respondents, using anchoring vignettes to adjust for reporting heterogeneity, i.e., cross-national differences in use of response categories. Methods: Study participants, ages 20 to 59, were recruited from online survey panels retained by Embrain in Korea (N = 1170) and the US (N = 1033). In the analyses, we first examined the two key measurement assumptions of the anchoring vignette method. Response consistency was examined by regressing SRH on vignette ratings and EQ-5D, and was satisfied when the relationship between SRH and vignette ratings was significant and positive. Vignette equivalence was assessed by examining whether respondents correctly rank-ordered vignettes by health status severity. We then compared estimates of the between-country difference in SRH from two models: a standard ordered probit regression, and a hierarchical ordered probit (Hopit) regression, which adjusted for cross-country differences in use of response categories. Results: The anchoring vignettes satisfied both measurement assumptions. Results from the ordered probit regression indicated that Korean SRH was worse than that in the US. However, results from the Hopit regression revealed that Korean SRH was actually better than that in the US, after adjusting for Korean respondents’ significantly higher intercategory thresholds (demarcating between “very bad” and “bad,” “bad” and “fair,” etc.). Conclusion: The apparently lower SRH of Korean vis-à-vis US respondents is an artifact of Koreans’ higher standards for health-related response categories. After adjusting for these different standards, Korean SRH is revealed to be higher than US SRH.