Tax-based systems finance healthcare through taxes collected from the entire population of taxpayers, allowing risks to be pooled across a large group. This subsidizes care for the poor and sick by transferring wealth from the rich and healthy. However, overuse of free services remains a problem. Pay-as-you-go user fee systems represent a market-based solution but fees disproportionately reduce access for the poor. Risk-based private insurance guarantees entitlement by collecting risk-adjusted premiums but rising costs can cause the poor and sick to lose coverage. Social health insurance compulsorily collects premiums from a broad base to ensure universal coverage unlike private systems. Donor funding significantly finances developing countries' healthcare through government systems or private organizations.