Effect of mass transfers of enrollees from liquidated health insurance companies on the financial sustainability of health insurance: an ecological study in the Colombian health system

BACKGROUND: The liquidation of health promoting entities (Entidades Promotoras de Salud (EPS)) in Colombia and the forced transfer of millions of enrollees to solvent insurers have raised concerns about the financial sustainability of the health insurance system. This study examines the impact of these uncompensated mass transfers on key financial indicators of receiving EPS. METHODS: A multitemporal ecological study and a difference-in-differences (DiD) model were conducted using national administrative data. Nine continuously operating EPS that received enrollees from liquidated entities were included. Key financial indicators analysed included operating margin, capitation payment unit (Unidad de Pago por Capitación (UPC)) sufficiency, medical loss ratio, per capita medical cost and enrolment volume. Linear mixed-effects and fixed-effects DiD models were applied. FINDINGS: Average operating margins decreased from 3.2% (2017) to -0.59% (2024). In mixed-effects models, UPC sufficiency was the strongest positive correlate of margin (β=0.28, 95% CI 0.14 to 0.41), while per capita medical cost (β=-0.43, 95% CI -0.66 to -0.21) and enrollee transfers (β=-0.014, 95% CI -0.027 to -0.002) were negatively associated. DiD estimates show that mass transfers reduced operating margins by 1.2 percentage points (95% CI -1.5 to -0.9), with the strongest effects in the first 2 years and consistent results across sensitivity analyses. INTERPRETATION: Uncompensated mass enrollee transfers from liquidated EPS have a significant negative impact on the financial sustainability of receiving insurers. Regulatory reforms, including risk-adjusted premium adjustments and interinsurer compensation mechanisms, are urgently needed.