Key factors associated with China’s basic medical insurance fund revenue-expenditure balance: a grey relational analysis

The financial equilibrium of China’s Basic Medical Insurance Fund (BMIF) is pivotal, as it directly influences the sustainability, equity, and stability of the healthcare security system. Nevertheless, rapid population aging, increasing burdens chronic diseases, and rising hospitalization rates pose growing threats to this balance. Therefore, identifying key factors affecting the BMIF’s fiscal balance and developing targeted regulatory strategies are of considerable theoretical and practical significance. Using national data from 2018 to 2023, Grey Relational Analysis (GRA) was employed to assess the correlation between BMIF revenue–expenditure balance and several indicators: insured population metrics, medical fund revenue patterns, healthcare utilization trends and associated costs, and reimbursement ratios. For the Urban Employees’ Basic Medical Insurance (UEBMI) fund, revenue-expenditure balance was most strongly associated with hospitalization utilization (grey correlation degree = 0.940), reimbursement ratio (0.925), and cross-regional medical treatment (0.916). Fund income growth (0.805) and insured population growth (0.838) shown moderate correlations, while the growth of hospitalization costs (0.611) had the weaker association. In contrast, the revenue-expenditure balance of the Urban and Rural Residents’ Basic Medical Insurance (URRBMI) fund was most closely linked to reimbursement ratio(0.814), hospitalization utilization (0.804), and fund income growth rate (0.802). Cross-regional medical visits (0.777) and hospitalization costs (0.736) demonstrated moderate associations, while insured population growth (0.578) exhibited a negligible relationship. The financial equilibrium of UEBMI and URRBMI funds is associated with distinct primary factors: service utilization patterns and cost-sharing mechanisms exhibit the strongest associations for UEBMI, while URRBMI shows the highest grey relational degree with—though utilization and reimbursement rates remain importantly associated. To promote sustainable fiscal balance across both funds, coordinated policies that target these key associated factors are essential, such as those aimed at hospitalization demand, optimizing reimbursement structures, and managing cross-regional care. Additionally, implementing income-based subsidy schemes and contribution mechanisms could be a viable strategy for enhancing URRBMI’s financial resilience, as our analysis indicates a strong association between revenue fluctuations and its balance.