Adverse selection

Insurance companies use the term "adverse selection" to describe the tendency for only those who will benefit from insurance to buy it. Specifically when talking about health insurance, unhealthy people are more likely to purchase health insurance because they anticipate large medical bills. On the other side, people who consider themselves to be reasonably healthy may decide that medical insurance is an unnecessary expense; if they see the doctor once a year and it costs $250, that's much better than making monthly insurance payments of $40. (example figures).

The fundamental concept of insurance is that it balances costs across a large, random sample of individuals (see risk pool). For instance, an insurance company has a pool of 1000 randomly selected subscribers, each paying $100 per month. One person becomes very ill while the others stay healthy, allowing the insurance company to use the money paid by the healthy people to pay for the treatment costs of the sick person. However, when the pool is self-selecting rather than random, as is the case with individuals seeking to purchase health insurance directly, adverse selection is a greater concern.[12] A disproportionate share of health care spending is attributable to individuals with high health care costs. In the US the 1% of the population with the highest spending accounted for 27% of aggregate health care spending in 1996. The highest-spending 5% of the population accounted for more than half of all spending. These patterns were stable through the 1970s and 1980s, and some data suggest that they may have been typical of the mid-to-early 20th century as well.[13][14] A few individuals have extremely high medical expenses, in extreme cases totaling a half million dollars or more.[15] Adverse selection could leave an insurance company with primarily sick subscribers and no way to balance out the cost of their medical expenses with a large number of healthy subscribers.

Because of adverse selection, insurance companies employ medical underwriting, using a patient's medical history to screen out those whose pre-existing medical conditions pose too great a risk for the risk pool. Before buying health insurance, a person typically fills out a comprehensive medical history form that asks whether the person smokes, how much the person weighs, whether the person has been treated for any of a long list of diseases and so on. In general, those who present large financial burdens are denied coverage or charged high premiums to compensate.[16] One large US industry survey found that roughly 13 percent of applicants for comprehensive, individually purchased health insurance who went through the medical underwriting in 2004 were denied coverage. Declination rates increased significantly with age, rising from 5 percent for individuals 18 and under to just under a third for individuals aged 60 to 64.[17] Among those who were offered coverage, the study found that 76% received offers at standard premium rates, and 22% were offered higher rates.[18] On the other side, applicants can get discounts if they do not smoke and are healthy.[19]