Health insurance is an insurance that covers the whole or a part of the risk of a person incurring medical expenses, spreading the risk over a large number of persons. By estimating the overall risk of health care and health system expenses over the risk pool, an insurer can develop a routine finance structure, such as a monthly premium or payroll tax, to provide the money to pay for the health care benefits specified in the insurance agreement.[1] The benefit is administered by a central organization such as a government agency, private business, or not-for-profit entity.
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.
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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.
Medicare Advantage plans expand the health insurance options for people with Medicare. Medicare Advantage was created under the Balanced Budget Act of 1997, with the intent to better control the rapid growth in Medicare spending, as well as to provide Medicare beneficiaries more choices. But on average, Medicare Advantage plans cost 12% more than traditional Medicare.[48] The ACA took steps to align payments to Medicare Advantage plans with the cost of traditional Medicare.
While politically difficult, some politicians and observers have argued for a single-payer system.[30] A bill, the United States National Health Care Act, was first proposed by Representative John Conyers in 2003[31] and has been perennially proposed since, including during the debate on the public option and the Patient Protection and Affordable Care Act.[32] President Obama has come out against a single-payer reform at this time, stating in the joint session of Congress that "it makes more sense to build on what works and fix what doesn't, rather than try to build an entirely new system from scratch."[33] Obama had previously expressed that he is a proponent of a single payer universal health care program during an AFL-CIO conference in 2003.[34]
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.
States regulate small group premium rates, typically by placing limits on the premium variation allowable between groups (rate bands). Insurers price to recover their costs over their entire book of small group business while abiding by state rating rules.[74] Over time, the effect of initial underwriting "wears off" as the cost of a group regresses towards the mean. Recent claim experience—whether better or worse than average—is a strong predictor of future costs in the near term. But the average health status of a particular small employer group tends to regress over time towards that of an average group.[75] The process used to price small group coverage changes when a state enacts small group reform laws.[76]
The 1960 Kerr-Mills Act provided matching funds to states assisting patients with their medical bills. In the early 1960s, Congress rejected a plan to subsidize private coverage for people with Social Security as unworkable, and an amendment to the Social Security Act creating a publicly run alternative was proposed. Finally, President Lyndon B. Johnson signed the Medicare and Medicaid programs into law in 1965, creating publicly run insurance for the elderly and the poor.[29] Medicare was later expanded to cover people with disabilities, end-stage renal disease, and ALS.
The Blue Cross Blue Shield Association (BCBSA) is a federation of 38 separate health insurance organizations and companies in the United States. Combined, they directly or indirectly provide health insurance to over 100 million Americans.[92] BCBSA insurance companies are franchisees, independent of the association (and traditionally each other), offering insurance plans within defined regions under one or both of the association's brands. Blue Cross Blue Shield insurers offer some form of health insurance coverage in every U.S. state, and also act as administrators of Medicare in many states or regions of the United States, and provide coverage to state government employees as well as to federal government employees under a nationwide option of the Federal Employees Health Benefit Plan.[93]
^ Bump, Jesse B. (19 October 2010). "The long road to universal health coverage. A century of lessons for development strategy" (PDF). Seattle: PATH. Retrieved 10 March 2013. Carrin and James have identified 1988—105 years after Bismarck's first sickness fund laws—as the date Germany achieved universal health coverage through this series of extensions to minimum benefit packages and expansions of the enrolled population. Bärnighausen and Sauerborn have quantified this long-term progressive increase in the proportion of the German population covered by public and private insurance. Their graph is reproduced below as Figure 1: German Population Enrolled in Health Insurance (%) 1885–1995.
Premiums, or the cost of the medical coverage, are based on some factors including country of origin, age, medical history, etc. It is advised to have more comprehensive insurance for US medical coverage because it can cost a lot, but the costs of not having it can be much higher. For example, the tests and scans doctors often run are costly and typically not covered by budget medical insurance plans.
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]
As far as the compulsory health insurance is concerned, the insurance companies cannot set any conditions relating to age, sex or state of health for coverage. Although the level of premium can vary from one company to another, they must be identical within the same company for all insured persons of the same age group and region, regardless of sex or state of health. This does not apply to complementary insurance, where premiums are risk-based.
For periods of less than one year in the US, a travel medical plan may be enough to cover your needs. For younger travelers wanting basic emergency medical insurance (instead of comprehensive major medical cover), a travel medical plan will work well. Most travel medical insurance plans provide coverage for accidents or illness, saving you from large medical bills if you require a visit to the doctor or hospital while in the U.S. as well as give you access to universal pharmaceutical care and translation services, should they be required. For more, see:
Types of Coverage: All of the health plans sold through the Marketplace are offered by private insurance companies and are required to meet minimum requirements. All of the plans are required to cover a comprehensive set of benefits that includes hospital care, doctors’ visits, emergency care, prescription drugs, lab services, preventive care, and rehabilitative services. Before choosing a plan, individuals will be able to see whether their healthcare practitioner participates in the plan’s network (if choosing a network plan). Individuals will be able to choose the plan that best meets their needs and budget. Individuals with low-incomes may instead qualify for free or low-cost coverage through Medicaid or the Children’s Health Insurance Program. 
For periods of less than one year in the US, a travel medical plan may be enough to cover your needs. For younger travelers wanting basic emergency medical insurance (instead of comprehensive major medical cover), a travel medical plan will work well. Most travel medical insurance plans provide coverage for accidents or illness, saving you from large medical bills if you require a visit to the doctor or hospital while in the U.S. as well as give you access to universal pharmaceutical care and translation services, should they be required. For more, see:

Traveling abroad is exciting. Living abroad, especially in the USA, is a whole different level of adventure. An expatriate also called an expat, is a person who has left their home country to live somewhere else. The transition to a new country comes with challenges. One of those challenges is securing adequate international health insurance to cover you in the United States as well as your home country and other countries you may travel to.

President Harry S. Truman proposed a system of public health insurance in his November 19, 1945, address. He envisioned a national system that would be open to all Americans, but would remain optional. Participants would pay monthly fees into the plan, which would cover the cost of any and all medical expenses that arose in a time of need. The government would pay for the cost of services rendered by any doctor who chose to join the program. In addition, the insurance plan would give cash to the policy holder to replace wages lost because of illness or injury. The proposal was quite popular with the public, but it was fiercely opposed by the Chamber of Commerce, the American Hospital Association, and the AMA, which denounced it as "socialism".[25]