Macroeconomic shock-response functions of health system resilience and equity: a global simulation study.

To quantify how macroeconomic shocks propagate into health system resilience and equity, we develop a globally comparable stress-testing framework isolating within-country responses to standardised shocks. Using a panel of 205 countries (2000-2022; 3,009 observations) with harmonised World Bank data, we construct three indices: Economic Shock, Health System Resilience and Health Equity. Symmetric ±5%, ±10% and ±20% shocks generate counterfactual scenarios, with responses estimated via simulation and validated using linear elasticity, Random Forest and XGBoost. Macroeconomic shocks produce predictable, monotonic shifts in the Economic Shock Index with limited cross-country dispersion, ensuring clean variation. Adverse shocks lead to statistically significant declines in both resilience and equity, with all 95% confidence intervals excluding zero. A -20% shock reduces resilience by 0.059 (95% CI: -0.060 to -0.059) and equity by 0.050 (95% CI: -0.051 to -0.050), while a + 20% shock increases resilience by 0.037 and equity by 0.032. Negative shocks generate approximately 60% larger absolute effects than positive shocks. Machine-learning results show near-linear responses under moderate shocks and bounded nonlinearities in severe downturns. Equity responds more strongly than resilience, indicating financial protection as the most vulnerable margin. Findings support protecting pooled financing and highlight simulation-based stress testing for anticipatory health policy.