PPO (Preferred Provider Organization) - A type of insurance plan that offers more extensive coverage for the services of healthcare providers who are part of the plan's network, but still offers some coverage for providers who are not part of the plan's network. PPO plans generally offer more flexibility than HMO plans, but premiums tend to be higher.
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. The US Department of Justice has recognized this percentage of market control as conferring substantial monopsony power in the relations between insurer and physicians.
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. 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. The Affordable Care Act took some steps to reduce Medicare spending, and various other proposals are circulating to reduce it further.
In general, the amount the employer must include is the amount by which the fair market value of the benefits is more than the sum of what the employee paid for it plus any amount that the law excludes. There are other special rules that employers and employees may use to value certain fringe benefits. See Publication 15-B, Employers' Tax Guide to Fringe Benefits, for more information.
However, with the Patient Protection and Affordable Care Act, effective since 2014, federal laws have created some uniformity in partnership with the existing state-based system. Insurers are prohibited from discriminating against or charging higher rates for individuals based on pre-existing medical conditions and must offer a standard set of coverage.
Coverage limits: Some health insurance policies only pay for health care up to a certain dollar amount. The insured person may be expected to pay any charges in excess of the health plan's maximum payment for a specific service. In addition, some insurance company schemes have annual or lifetime coverage maxima. In these cases, the health plan will stop payment when they reach the benefit maximum, and the policy-holder must pay all remaining costs.
Eligibility: Individuals who need coverage who are legally residing in the U.S. and who are not incarcerated are eligible to purchase coverage through their state’s Marketplace. Small employers with fewer than 50 full-time employers can also purchase coverage through the Marketplace. Insurance companies will not be allowed to deny coverage to individuals with pre-existing medical conditions nor will they be allowed to charge higher premiums to people because of their health status.
Another distinction between plans that can change the rates you pay, is the type of network the plan uses. Depending on whether the plan is a PPO, HMO, EPO or POS plan, consumers will have access to the health care providers managed in different ways. HMOs tend to be the most restrictive about which doctors you can see and what you must do to see them. This usually means that the insurers save on your cost of care and thereby provide lower premiums.
Most aspects of private health insurance in Australia are regulated by the Private Health Insurance Act 2007. Complaints and reporting of the private health industry is carried out by an independent government agency, the Private Health Insurance Ombudsman. The ombudsman publishes an annual report that outlines the number and nature of complaints per health fund compared to their market share 
If you are an expatriate living in the US, additional medical coverage should be purchased for the period that you will be in the country. You will want to ensure this coverage protects you in case of an accident, a medical emergency as well as repatriation. You should investigate if you will need this insurance before entering the country and if the insurance needs to come from your home country, the U.S. or both!
Since people who lack health insurance are unable to obtain timely medical care, they have a 40% higher risk of death in any given year than those with health insurance, according to a study published in the American Journal of Public Health. The study estimated that in 2005 in the United States, there were 45,000 deaths associated with lack of health insurance. A 2008 systematic review found consistent evidence that health insurance increased utilization of services and improved health.