''...rampant and persistent asymmetric information in a market can lead to its collapse. Consider a used car market where the sellers know the quality of their cars, but the buyers cannot distinguish between lemons (bad cars) and peaches (good cars).
In such a market, buyers will want to pay only an average-quality price for the cars on the market, since they can’t tell the difference between peaches and lemons. Sellers who know their cars are peaches, however, will not want to sell them in this market because they know their cars are worth more than the average price. As they pull their peaches out of the market, the average quality drops and, in turn, the price of the used cars left in the market keeps dropping. The sellers of lemons freeride on the market until it collapses into just a market of lemons.
Adverse selection was an early concern with the state health insurance exchanges as part of the Affordable Care Act (ACA) in the United States. Extending the metaphor, the lemons are sick people applying to the exchanges, and the peaches are healthy people applying. There was an individual mandate requiring health insurance, but the penalties for not complying were low, so the concern was that many healthy people would just opt to pay the fine rather than participate. Sick people, who need the insurance, would therefore make up more of the applicants, causing premiums to rise so that health insurers could cover their costs to care for them. This would, in turn, eject from the market more healthy participants not willing to pay these higher premiums, further raising prices. This situation is still unfolding, with those invested in the success of the ACA trying to ensure that it doesn’t spiral out of control.''