Asymmetric Information, Adverse Selection, and Moral Hazard

Introduction

Welcome to our lesson on the final major type of market failure in this module: asymmetric information. In our previous lessons, we explored market failures arising from externalities (like pollution), public goods (like national defense), and common resources (like open-ocean fisheries). In all those cases, we implicitly assumed that buyers and sellers had roughly the same information.

Today, we will relax that assumption. We will explore what happens when one side of a market knows something crucial that the other side doesn't. This imbalance, called asymmetric information, can prevent markets from reaching efficient outcomes, creating its own distinct form of market failure.

Our learning outcome is to describe how asymmetric information can cause adverse selection and moral hazard. We will unpack these two core problems, using classic examples like used cars and insurance markets to see how they play out in the real world.

1. The Two Faces of Asymmetric Information

Asymmetric information generally leads to two distinct problems, and the key difference is when the problem occurs relative to a transaction or contract.

• Adverse Selection: A problem of hidden characteristics that exists before the transaction. The mix of people or goods attracted to a deal is "adversely selected" from the perspective of the less-informed party.
• Moral Hazard: A problem of hidden action that occurs after the transaction. A contract or agreement changes one party's incentives, leading them to behave in ways that are costly to the other party.

To get a clear, high-level overview of this crucial distinction, please watch the beginning of the following video.

2. Adverse Selection: The Problem of Hidden Characteristics

Adverse selection arises when the "type" or "quality" of what's being traded is hidden from one party. This can lead to a downward spiral where high-quality goods or low-risk individuals are driven out of the market.

The "Market for Lemons"

The classic illustration of adverse selection comes from Nobel laureate George Akerlof's 1970 paper on the market for used cars. He demonstrated how asymmetric information could cause the market to malfunction, or even collapse entirely.

The video below explains Akerlof's "lemons problem" in detail.

As the video illustrates, the core issue is that buyers, unable to assess a specific car's quality, are only willing to pay a price that reflects the average quality of all used cars on the market. This average price might be unacceptably low for someone selling a high-quality car. Consequently, sellers of good cars leave the market. This exodus lowers the average quality of the remaining cars, which in turn lowers the price buyers are willing to pay, pushing even more sellers out. In the extreme, only the "lemons" remain, and the market fails.

Adverse Selection in Insurance Markets

The same logic applies powerfully to insurance markets, but here, the information asymmetry is reversed: the buyer has more information than the seller.

• The Buyer's Hidden Information: You know more about your health (if you're a safe or risky person, your family's medical history, etc.) than the health insurance company does.
• The Insurer's Problem: The insurer sets a premium based on the expected costs of an average person in the applicant pool.
• The Selection Effect: This average premium will seem like a great deal to high-risk (less healthy) people but a bad deal to low-risk (very healthy) people. As a result, high-risk individuals are more likely to buy insurance, while low-risk individuals opt out.

This leads to the infamous insurance "death spiral": as healthy people leave, the average risk of the pool increases, forcing insurers to raise premiums. Higher premiums cause even more healthy people to leave, and the cycle continues until insurance becomes unaffordably expensive, or the market collapses.

This is a major reason why employer-provided health insurance is so common. By insuring an entire group of working people (a mix of healthy and less-healthy individuals not selected based on their health status), insurers can overcome the adverse selection problem. Government mandates, like the individual mandate in the Affordable Care Act, serve a similar purpose by forcing everyone into the pool.

3. Moral Hazard: The Problem of Hidden Action

Now let's turn to moral hazard. This occurs after a contract is signed, when one party is insulated from risk and changes their behavior. The term "moral" here doesn't imply a judgment of right or wrong; it's an older term referring to behavior or conduct.

How Insurance Changes Behavior

Insurance is the classic setting for moral hazard. Once you are insured, the cost associated with a negative outcome is reduced, which can subtly change your behavior.

• If you have comprehensive car insurance, you might be less vigilant about where you park your car.
• If your health insurance fully covers all costs, you might be more likely to agree to expensive treatments of marginal benefit.

Professor Gruber introduces this concept in the next clip.

A simple, non-insurance example helps build intuition. Imagine a group of ten friends agreeing to split a dinner bill equally before ordering. This "insurance" against ordering an expensive meal creates a moral hazard. Everyone has an incentive to order more than they normally would (e.g., an appetizer, a pricey steak, dessert) because they only have to pay one-tenth of its cost. The result is a much higher bill for everyone than if each person had paid for their own meal.

The Costs of Moral Hazard

Moral hazard creates inefficiency. Because insurance shields people from the true cost of their actions, they tend to "over-consume" safety, medical care, or leisure. Society ends up dedicating more resources to fixing problems than is socially optimal, because individuals have a reduced incentive to prevent those problems in the first place.

This creates a fundamental trade-off in designing insurance (both private and social):

• More generous insurance provides better protection against risk (which is good).
• ...but it also creates stronger moral hazard, leading to more inefficiency and higher costs (which is bad).

Solutions to moral hazard are designed to make the insured party retain some "skin in the game." In insurance, this includes:

• Deductibles: You pay the first $X of damages yourself.
• Co-payments/Co-insurance: You pay a fixed amount or percentage of every claim.
• Monitoring: The insurance company might offer a discount if you install a fire alarm or a tracking device in your car.

4. Summary: Adverse Selection vs. Moral Hazard

You have now seen both concepts in detail. To reinforce the distinction, let's summarize them in a table.

To see how both concepts can apply to a single market, consider the market for rental housing.

• Adverse Selection: People who are riskier tenants (e.g., messier, less responsible) might be more attracted to renting than buying a home. This is a pre-contract selection problem.
• Moral Hazard: Once a person has rented an apartment and paid a security deposit, they might be less careful about maintaining the property than if they owned it, because the landlord bears most of the long-term cost. This is a post-contract behavior problem.

Conclusion

In this lesson, we have moved beyond the assumption of perfect information and seen how markets can fail when one party knows more than another.

Key Takeaways:

• Asymmetric Information is a market condition where one party in a transaction has more information than the other, leading to inefficient outcomes.
• Adverse Selection is a problem of hidden characteristics that occurs before a transaction. It can lead to markets being dominated by low-quality goods or high-risk individuals, as seen in the "lemons problem" and health insurance markets.
• Moral Hazard is a problem of hidden action that occurs after a transaction. Being protected from risk (e.g., by insurance) incentivizes individuals to behave in ways that are riskier or more costly than they otherwise would.
• Solutions to these problems often involve mechanisms to either reveal information (screening), reduce the benefit of having private information (mandates), or re-expose the informed party to risk (deductibles and co-payments).

This lesson concludes our module on market failures. We have seen that while markets are powerful tools for allocating resources, they can fail in the presence of externalities, public goods, common resources, and asymmetric information.

In our next lesson, we will examine the last topic in this module: how governments intervene to correct a different kind of inefficiency, the one caused by a lack of competition. We'll explore how price regulation and antitrust policy are used to address monopoly power.