The shared responsibility provision is part of the Affordable Care Act, also known as ACA or Obamacare. The goal is to ensure that all US citizens and permanent residents have access to quality health insurance. Any non-resident aliens, including international students on F, J, M and Q visas (and certain family members of students) are not subject to the individual mandate for their first 5 years in the U.S. All other J categories (teacher, trainee, work and travel, au pair, high school, etc.) are not subject to the individual mandate for 2 years (out of the past six).
Funding from the equalization pool is distributed to insurance companies for each person they insure under the required policy. However, high-risk individuals get more from the pool, and low-income persons and children under 18 have their insurance paid for entirely. Because of this, insurance companies no longer find insuring high risk individuals an unappealing proposition, avoiding the potential problem of adverse selection.

The UK's National Health Service (NHS) is a publicly funded healthcare system that provides coverage to everyone normally resident in the UK. It is not strictly an insurance system because (a) there are no premiums collected, (b) costs are not charged at the patient level and (c) costs are not pre-paid from a pool. However, it does achieve the main aim of insurance which is to spread financial risk arising from ill-health. The costs of running the NHS (est. £104 billion in 2007-8)[39] are met directly from general taxation. The NHS provides the majority of health care in the UK, including primary care, in-patient care, long-term health care, ophthalmology, and dentistry.
Before the development of medical expense insurance, patients were expected to pay 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. One major obstacle to this development was that early forms of comprehensive health insurance were enjoined by courts for violating the traditional ban on corporate practice of the professions by for-profit corporations.[66] State legislatures had to intervene and expressly legalize health insurance as an exception to that traditional rule. Today, most comprehensive private health insurance programs cover the cost of routine, preventive, and emergency health care procedures, and most prescription drugs (but this is not always the case).
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]
The US health insurance market is highly concentrated, as leading insurers have carried out over 400 mergers from the mid-1990s to the mid-2000s (decade). In 2000, the two largest health insurers (Aetna and UnitedHealth Group) had total membership of 32 million. By 2006 the top two insurers, WellPoint (now Anthem) and UnitedHealth, had total membership of 67 million. The two companies together had more than 36% of the national market for commercial health insurance. The AMA has said that it "has long been concerned about the impact of consolidated markets on patient care." A 2007 AMA study found that in 299 of the 313 markets surveyed, one health plan accounted for at least 30% of the combined health maintenance organization (HMO)/preferred provider organization (PPO) market. In 90% of markets, the largest insurer controls at least 30% of the market, and the largest insurer controls more than 50% of the market in 54% of metropolitan areas.[116] The US Department of Justice has recognized this percentage of market control as conferring substantial monopsony power in the relations between insurer and physicians.[117]
A 2011 study found that there were 2.1 million hospital stays for uninsured patients, accounting for 4.4% ($17.1 billion) of total aggregate inpatient hospital costs in the United States.[12] The costs of treating the uninsured must often be absorbed by providers as charity care, passed on to the insured via cost-shifting and higher health insurance premiums, or paid by taxpayers through higher taxes.[13]
Coinsurance: Instead of, or in addition to, paying a fixed amount up front (a co-payment), the co-insurance is a percentage of the total cost that insured person may also pay. For example, the member might have to pay 20% of the cost of a surgery over and above a co-payment, while the insurance company pays the other 80%. If there is an upper limit on coinsurance, the policy-holder could end up owing very little, or a great deal, depending on the actual costs of the services they obtain.
Still, private insurance remained unaffordable or simply unavailable to many, including the poor, the unemployed, and the elderly. Before 1965, only half of seniors had health care coverage, and they paid three times as much as younger adults, while having lower incomes.[28] Consequently, interest persisted in creating public health insurance for those left out of the private marketplace.
Carrin, Guy; James, Chris (January 2005). "Social health insurance: Key factors affecting the transition towards universal coverage" (PDF). International Social Security Review. 58 (1): 45–64. doi:10.1111/j.1468-246x.2005.00209.x. Retrieved 10 March 2013. Initially the health insurance law of 1883 covered blue-collar workers in selected industries, craftspeople and other selected professionals.6 It is estimated that this law brought health insurance coverage up from 5 to 10 per cent of the total population.
Between October 28 and November 13, 2009, Democratic Senator Dick Durbin's campaign organization polled Americans to rank their support for various forms of the "public option" currently under consideration by Congress for inclusion in the final health care reform bill. The 83,954 respondents assigned rankings of 0 to 10. A full national option had the most support, with an 8.56 average, while no public option was least favored, with a 1.10 average.[52]
Health insurance can be tricky to navigate. Managed care insurance plans require policyholders to receive care from a network of designated health care providers for the highest level of coverage. If patients seek care outside the network, they must pay a higher percentage of the cost. In some cases, the insurance company may even refuse payment outright for services obtained out of network. Many managed care plans require patients to choose a primary care physician who oversees the patient's care and makes recommendations about treatment. Insurance companies may also deny coverage for services that were obtained without preauthorization. In addition, insurers may refuse payment for name-brand drugs if a generic version or comparable medication is available at a lower cost.
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]