Dynamic effects of outpatient pooling scheme on socioeconomic inequality in healthcare utilization in China from 2011 to 2020.

Despite achieving universal health coverage (UHC), socioeconomic inequalities in healthcare utilization persist in China, particularly in outpatient care, due to limited financial protection. To address this gap, the Chinese government introduced an outpatient pooling scheme under the Urban Employee Basic Medical Insurance (UEBMI), aimed at reducing cost-sharing burdens. This study evaluates the policy's impact on socioeconomic disparities in outpatient care utilization from 2011 to 2020, providing critical insights into the role of insurance reforms in promoting health equity. Leveraging nationally representative longitudinal data from five waves (2011-2020) of the China Health and Retirement Longitudinal Study (CHARLS), we employed a quasi-experimental design to assess outpatient care utilization across multiple dimensions: visit probability, facility type (hospitals vs. primary care), expenditures, and out-of-pocket (OOP) payments. Propensity score matching (PSM) was utilized to mitigate selection bias, creating balanced cohorts between policy-implementing and non-implementing regions. Socioeconomic inequality was quantified using concentration indices (CI), and decomposition analyses were conducted to isolate the policy's contribution to temporal changes in inequality. The outpatient pooling scheme significantly reduced pro-rich inequality in outpatient visits, with the CI decreasing from 0.1142 in 2011 to 0.0972 in 2020, and the policy contributing 4.14% to this decline. However, disparities in facility utilization widened: the CI for hospital visits increased from 0.0069 to 0.0431, while primary care visits shifted from 0.0064 to -0.1091, indicating growing pro-poor inequality in primary care use. Despite persistent pro-rich inequalities in expenditures and OOP payments, their CI values declined substantially, with the policy playing a key role in driving this equitable trend. Notably, the policy's counteractive effects mitigated the worsening disparities in facility utilization over time. The outpatient pooling scheme effectively reduced pro-rich inequalities in outpatient care access and expenditures, demonstrating its potential to enhance financial protection for low-income populations. However, the widening gaps in facility utilization highlight the need for complementary interventions, such as improving primary care quality and optimizing resource allocation, to address systemic inequalities. These findings underscore the importance of integrating financial reforms with structural improvements to achieve equitable healthcare delivery in China and other low- and middle-income countries.