Employer-sponsored health insurance plans dramatically expanded as a direct result of wage controls imposed by the federal government during World War II.[20] The labor market was tight because of the increased demand for goods and decreased supply of workers during the war. Federally imposed wage and price controls prohibited manufacturers and other employers from raising wages enough to attract workers. When the War Labor Board declared that fringe benefits, such as sick leave and health insurance, did not count as wages for the purpose of wage controls, employers responded with significantly increased offers of fringe benefits, especially health care coverage, to attract workers.[20]
As the population covered by Medicare grows, its costs are projected to rise from slightly over 3 percent of GDP to over 6 percent, contributing substantially to the federal budget deficit.[47] In 2011, Medicare was the primary payer for an estimated 15.3 million inpatient stays, representing 47.2 percent ($182.7 billion) of total aggregate inpatient hospital costs in the United States.[12] The Affordable Care Act took some steps to reduce Medicare spending, and various other proposals are circulating to reduce it further.
The United States health care system relies heavily on private health insurance, which is the primary source of coverage for most Americans. As of 2012 about 61% of Americans had private health insurance according to the Centers for Disease Control and Prevention.[56] The Agency for Healthcare Research and Quality (AHRQ) found that in 2011, private insurance was billed for 12.2 million U.S. inpatient hospital stays and incurred approximately $112.5 billion in aggregate inpatient hospital costs (29% of the total national aggregate costs).[57] Public programs provide the primary source of coverage for most senior citizens and for low-income children and families who meet certain eligibility requirements. The primary public programs are Medicare, a federal social insurance program for seniors and certain disabled individuals; and Medicaid, funded jointly by the federal government and states but administered at the state level, which covers certain very low income children and their families. Together, Medicare and Medicaid accounted for approximately 63 percent of the national inpatient hospital costs in 2011.[57] SCHIP is a federal-state partnership that serves certain children and families who do not qualify for Medicaid but who cannot afford private coverage. Other public programs include military health benefits provided through TRICARE and the Veterans Health Administration and benefits provided through the Indian Health Service. Some states have additional programs for low-income individuals.[58]
Having health insurance is important for several reasons. Uninsured people receive less medical care and less timely care, they have worse health outcomes, and lack of insurance is a fiscal burden for them and their families. Moreover, the benefits of expanding coverage outweigh the costs for added services. Safety-net care from hospitals and clinics improves access to care but does not fully substitute for health insurance. These findings are supported by much research, although some cautions are appropriate in using these results.
In the United States, Medicare is a federal social insurance program that provides health insurance to people over the age of 65, individuals who become totally and permanently disabled, end stage renal disease (ESRD) patients, and people with ALS. Recent research has found that the health trends of previously uninsured adults, especially those with chronic health problems, improves once they enter the Medicare program.[45] Traditional Medicare requires considerable cost-sharing, but ninety percent of Medicare enrollees have some kind of supplemental insurance—either employer-sponsored or retiree coverage, Medicaid, or a private Medigap plan—that covers some or all of their cost-sharing.[46] With supplemental insurance, Medicare ensures that its enrollees have predictable, affordable health care costs regardless of unforeseen illness or injury.
Generally, group health insurance plans cover the cost of medical office visits for illness and checkups, hospitalization, emergency room services, ambulance transportation, operations, physical therapy, and even prescription drugs, to provide several examples of potentially covered health care services. But, every plan is different and it behooves an employee to become familiar with the details of his or her employer's plan before the benefit is needed.
According to a 2007 study, about 59% of employers at small firms (3–199 workers) in the US provide employee health insurance. The percentage of small firms offering coverage has been dropping steadily since 1999. The study notes that cost remains the main reason cited by small firms who do not offer health benefits.[66] Small firms that are new are less likely to offer coverage than ones that have been in existence for a number of years. For example, using 2005 data for firms with fewer than 10 employees, 43% of those that had been in existence at least 20 years offered coverage, but only 24% of those that had been in existence less than 5 years did. The volatility of offer rates from year to year also appears to be higher for newer small businesses.[67]

Historically, health insurance has been regulated by the states, consistent with the McCarran-Ferguson Act. Details for what health insurance could be sold were up to the states, with a variety of laws and regulations. Model acts and regulations promulgated by the National Association of Insurance Commissioners (NAIC) provide some degree of uniformity state to state. These models do not have the force of law and have no effect unless they are adopted by a state. They are, however, used as guides by most states, and some states adopt them with little or no change.
Other managed care techniques include such elements as disease management, case management, wellness incentives, patient education, utilization management and utilization review. These techniques can be applied to both network-based benefit programs and benefit programs that are not based on a provider network. The use of managed care techniques without a provider network is sometimes described as "managed indemnity."
Early hospital and medical plans offered by insurance companies paid either a fixed amount for specific diseases or medical procedures (schedule benefits) or a percentage of the provider's fee. The relationship between the patient and the medical provider was not changed. The patient received medical care and was responsible for paying the provider. If the service was covered by the policy, the insurance company was responsible for reimbursing or indemnifying the patient based on the provisions of the insurance contract ("reimbursement benefits"). Health insurance plans that are not based on a network of contracted providers, or that base payments on a percentage of provider charges, are still described as indemnity or fee-for-service plans.[19]
However, in a 2007 analysis, the Employee Benefit Research Institute concluded that the availability of employment-based health benefits for active workers in the US is stable. The "take-up rate," or percentage of eligible workers participating in employer-sponsored plans, has fallen somewhat, but not sharply. EBRI interviewed employers for the study, and found that others might follow if a major employer discontinued health benefits. Effective by January 1, 2014, the Patient Protection and Affordable Care Act will impose a $2000 per employee tax penalty on employers with over 50 employees who do not offer health insurance to their full-time workers. (In 2008, over 95% of employers with at least 50 employees offered health insurance.[63])[64] On the other hand, public policy changes could also result in a reduction in employer support for employment-based health benefits.[65]
In addition to such public plans as Medicare and Medicaid, the federal government also sponsors a health benefit plan for federal employees—the Federal Employees Health Benefits Program (FEHBP). FEHBP provides health benefits to full-time civilian employees. Active-duty service members, retired service members and their dependents are covered through the Department of Defense Military Health System (MHS). FEHBP is managed by the federal Office of Personnel Management.
The Affordable Care Act of 2010 was designed primarily to extend health coverage to those without it by expanding Medicaid, creating financial incentives for employers to offer coverage, and requiring those without employer or public coverage to purchase insurance in newly created health insurance exchanges. This requirement for almost all individuals to maintain health insurance is often referred to as the "individual mandate." The CBO has estimated that roughly 33 million who would have otherwise been uninsured will receive coverage because of the act by 2022.[17]