Medicare is a national social insurance program, administered by the U.S. federal government since 1966, currently using about 30-50 private insurance companies across the United States under contract for administration. United States Medicare is funded by a Payroll Tax, premiums and surtaxes from beneficiaries, and general revenue. It provides health insurance for Americans aged 65 and older who have worked and paid into the system through the payroll tax. It also provides health insurance to younger people with some disabilities status as determined by the Social Security Administration, as well as younger people with end stage renal disease and amyotrophic lateral sclerosis.
In 2015, Medicare provided health insurance for over 55 million—46 million people age 65 and older and nine million younger people. On average, Medicare covers about half of the health care charges for those enrolled. The enrollees must then cover their remaining costs either with supplemental insurance, separate insurance, or out-of-pocket. Out-of-pocket costs can vary depending on the amount of health care a Medicare enrollee needs. They might include the costs of uncovered services—such as for long-term, dental, hearing, and vision care—and supplemental insurance premiums.