Asymmetric information means one side of a transaction knows more than the other. In insurance, the customer usually knows more about their health, driving habits, or risk-taking behavior than the insurer. This creates two major problems: adverse selection and moral hazard.
Adverse selection: high-risk people are more likely to buy insurance
Adverse selection occurs before an insurance contract is signed.
Imagine a health insurance market with two groups:
- Low-risk people expect about $1,000 in medical costs each year.
- High-risk people expect about $10,000 in medical costs each year.
If insurers cannot tell which customers belong to which group, they may charge everyone an average premium, say $5,500.
What happens?
- High-risk people think this is a great deal because they expect to receive much more in benefits than they pay.
- Low-risk people think it's too expensive and decide not to buy insurance.
As healthier people leave the market, the remaining customers are riskier on average. Insurers then have to raise premiums again. That causes even more low-risk people to leave.
This repeating process is called the adverse selection death spiral:
- Insurer raises premiums.
- Low-risk customers drop coverage.
- Average risk rises.
- Premiums rise further.
- Even more healthy customers leave.
Eventually, the market may shrink dramatically or fail altogether, even though many people would have preferred insurance at a reasonable price.
Moral hazard: people behave differently after getting insurance
Moral hazard occurs after insurance is purchased.
Because insurance reduces the financial consequences of risky behavior, people may:
- Drive less carefully if fully insured.
- Visit doctors more often because someone else pays much of the bill.
- Take fewer precautions against loss.
This raises insurers' costs, which leads to higher premiums.
Insurers try to limit moral hazard through:
- Deductibles
- Copayments
- Coinsurance
- Monitoring
- Discounts for safe behavior
Why government regulation or mandates can help
Governments often intervene because insurance works best when the risk pool contains both low-risk and high-risk individuals.
Common policies include:
- Insurance mandates: Require most people—including healthy, low-risk individuals—to purchase insurance. This keeps the risk pool balanced and helps prevent adverse selection.
- Guaranteed issue: Require insurers to sell coverage regardless of health status.
- Community rating: Restrict how much insurers can vary premiums based on health.
- Subsidies: Help lower-income or healthier people afford premiums, encouraging broader participation.
Mandates and subsidies are often paired. For example, if insurers must cover everyone regardless of health but there is no incentive or requirement for healthy people to enroll, adverse selection can become more severe.
Without regulation
In a completely unregulated market:
- Insurers would try to avoid adverse selection by collecting extensive information, requiring medical exams, using detailed questionnaires, or charging highly individualized premiums.
- Some very high-risk people might face extremely high premiums or be denied coverage altogether.
- If insurers cannot accurately distinguish risk, markets may become unstable as low-risk customers opt out.
So the market does not necessarily disappear, but it may provide less insurance, exclude many high-risk individuals, or suffer from adverse selection if information remains imperfect.
The key idea
Insurance depends on pooling many people with different levels of risk. Asymmetric information makes it difficult for insurers to identify who is risky. When premiums reflect average risk rather than individual risk, healthier people are more likely to leave the market, increasing costs and potentially creating a cycle that can destabilize the insurance market. Government mandates, subsidies, and regulations are one set of tools for maintaining broad participation and reducing these information problems.
