in the united states, medicare is a national social insurance program, administered by the u.s. federal government since 1966, that guarantees access to health insurance for americans aged 65 and older who have worked and paid into the system, younger people with disabilities, and a few other groups. as a social insurance program, medicare spreads the financial risk associated with illness across society to protect everyone, and thus has a somewhat different social role from for-profit private insurers, which manage their risk portfolio by adjusting their pricing according to perceived risk.