From individual burden to social risk pooling: drivers of the declining out-of-pocket health expenditure share in China (2009–2024)

Reducing out-of-pocket payments (OOP) is central to equitable health financing. Although China’s OOP share has declined since 2009, it remains high internationally. This study analyzes the drivers of its reduction from 2009 to 2024. Using a multivariate time-series model, the OOP share is examined in relation to the share of social health expenditure, per capita GDP (log), aging rate, and urbanization rate. A structural breakpoint was identified using the Chow test and examined through subsample analysis. Aging increased the OOP share (coefficient = 1.094), while urbanization decreased it (coefficient = − 1.081). Social spending share showed no significant effect overall, but its association with OOP share reversed after 2016, becoming significantly positive during deepened reforms. China’s OOP share reduction results from aging (pressure) versus urbanization (relief). The post-2016 reversal between social spending share and OOP share highlights the phase-dependent nature of financing equity, demanding integrated policy responses.