Explaining changes in socioeconomic inequality in catastrophic health expenditure in China: a mobility-determinant decomposition.

backgroundCatastrophic health expenditure (CHE) remains a central challenge to achieving financial protection and equity in health systems. While extensive evidence shows that CHE remains disproportionately concentrated among socioeconomically disadvantaged households, most studies adopt a static perspective and provide limited insights into how CHE inequality evolves over time and through which mechanisms. This study aims to examine changes in socioeconomic inequality in CHE in China and disentangle the underlying channels from a household mobility perspective.

methodsUsing nationally representative longitudinal data from the 2010 and 2020 waves of the China Family Panel Studies, socioeconomic-related CHE inequality was measured using Erreygers' corrected concentration index, with household per capita wealth as the ranking variable. An integrated mobility-determinant decomposition framework was employed to quantify the contributions of both mobility processes and socioeconomic, demographic, and health system-related factors to changes in CHE inequality. Robustness analyses were performed using alternative CHE definitions, different specifications of household socioeconomic status, and an alternative decomposition approach.

resultsCHE remained disproportionately concentrated among lower-wealth households in both waves, although the magnitude of inequality declined significantly between 2010 and 2020. This reduction was primarily driven by progressive contribution of wealth-related CHE mobility, indicating larger improvements in financial protection among initially poorer households, while the regressive contribution of CHE-related wealth mobility partially offset these gains. Lower wealth quintiles, urban residence, and social health insurance coverage were associated with the reduction in CHE inequality, whereas higher wealth quintiles and household ageing were associated with attenuating the inequality reduction, reflecting heterogenous contributions through distinct mobility channels. Robustness checks confirmed the stability of the main findings.

conclusionsSocioeconomic inequality in CHE in China has narrowed over the past decade, primarily due to progressive improvements in financial protection. However, persistent wealth stratification and population ageing continue to constrain further reductions in CHE inequality. Monitoring progress toward universal health coverage requires attention not only to aggregate CHE incidence but also to the underlying mobility processes and structural determinants that influence distributional change.