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]

Health insurance primarily protects individuals from the prohibitively high costs of surgical procedures, inpatient hospital care, and emergency attention. Though health insurance itself can become costly for a family, it is only a small fraction of the potential costs associated with unforeseen illnesses and emergencies (for example, the diagnosis and treatment of cancer or a heart attack).
The remaining 45% of health care funding comes from insurance premiums paid by the public, for which companies compete on price, though the variation between the various competing insurers is only about 5%.[citation needed] However, insurance companies are free to sell additional policies to provide coverage beyond the national minimum. These policies do not receive funding from the equalization pool, but cover additional treatments, such as dental procedures and physiotherapy, which are not paid for by the mandatory policy.[citation needed]

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."
Americans are required to carry medical insurance that meets federally designated minimum standards or face a tax penalty. In certain cases, taxpayers may qualify for an exemption from the penalty if they were unable to obtain insurance due to financial hardship or other situations. Two public health insurance plans, Medicare and the Children's Health Insurance Program, target older individuals and children, respectively. Medicare also serves people with certain disabilities. The program is available to anyone age 65 or older. The CHIP plan has income limits and covers babies and children up to the age of 18.
If you are relocating the United States, it is important to know that the US does not require all expatriates (or US citizens) to have medical coverage. However, the risk of being in the US without medical coverage is massive hospital bills or even no access to medical care. There are newer requirements for certain expats on select visa types that may require you to have health coverage.

The public health insurance option, also known as the public insurance option or the public option, is a proposal to create a government-run health insurance agency that would compete with other private health insurance companies within the United States. The public option is not the same as publicly funded health care, but was proposed as an alternative health insurance plan offered by the government. The public option was initially proposed for the Patient Protection and Affordable Care Act, but was removed after Sen. Joe Lieberman (I-CT) threatened a filibuster.[1][2]
Public insurance cover increased from 2000–2010 in part because of an aging population and an economic downturn in the latter part of the decade. Funding for Medicaid and CHIP expanded significantly under the 2010 health reform bill.[9] The proportion of individuals covered by Medicaid increased from 10.5% in 2000 to 14.5% in 2010 and 20% in 2015. The proportion covered by Medicare increased from 13.5% in 2000 to 15.9% in 2010, then decreased to 14% in 2015.[3][10]