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]
Approximately 19 percent of Americans had coverage under Medicaid in 2016, and 14 percent had coverage under Medicare. These are government-run programs, as opposed to private coverage. However, the state and federal governments contract with private insurers to offer Medicaid managed care plans and Medicare Advantage plans, all of which are run by private insurers (in many cases, the same private insurers that offer employer-sponsored and individual market plans to the rest of the population).
According to some experts, such as Uwe Reinhardt,[120] Sherry Glied, Megan Laugensen,[121] Michael Porter, and Elizabeth Teisberg,[122] this pricing system is highly inefficient and is a major cause of rising health care costs. Health care costs in the United States vary enormously between plans and geographical regions, even when input costs are fairly similar, and rise very quickly. Health care costs have risen faster than economic growth at least since the 1970s. Public health insurance programs typically have more bargaining power as a result of their greater size and typically pay less for medical services than private plans, leading to slower cost growth, but the overall trend in health care prices have led public programs' costs to grow at a rapid pace as well.

Before the development of medical expense insurance, patients were expected to pay all other health care costs out of their own pockets, under what is known as the fee-for-service business model. During the middle to late 20th century, traditional disability insurance evolved into modern health insurance programs. Today, most comprehensive private health insurance programs cover the cost of routine, preventive, and emergency health care procedures, and also most prescription drugs, but this was not always the case. The rise of private insurance was accompanied by the gradual expansion of public insurance programs for those who could not acquire coverage through the market.
In 1935 the decision was made by the Roosevelt Administration not to include a large-scale health insurance program as part of the new Social Security program. The problem was not an attack by any organized opposition, such as the opposition from the American Medical Association that derailed Truman's proposals in 1949. Instead, there was a lack of active popular, congressional, or interest group support. Roosevelt's strategy was to wait for a demand and a program to materialize, and then if he thought it popular enough to throw his support behind it. His Committee on Economic Security (CES) deliberately limited the health segment of Social Security to the expansion of medical care and facilities. It considered unemployment insurance to be the major priority. Roosevelt assured the medical community that medicine would be kept out of politics. Jaap Kooijman says he succeeded in "pacifying the opponents without discouraging the reformers." The right moment never came for him to reintroduce the topic.[23][24]
Medicaid was instituted for the very poor in 1965. Since enrollees must pass a means test, Medicaid is a social welfare or social protection program rather than a social insurance program. Despite its establishment, the percentage of US residents who lack any form of health insurance has increased since 1994.[51] It has been reported that the number of physicians accepting Medicaid has decreased in recent years because of lower reimbursement rates.[52]
In addition to medical expense insurance, "health insurance" may also refer to insurance covering disability or long-term nursing or custodial care needs. Different health insurance provides different levels of financial protection and the scope of coverage can vary widely, with more than 40% of insured individuals reporting that their plans do not adequately meet their needs as of 2007.[2]