Information is the basis for our economic and financial decisions. As buyers, we collect information about products before entering into a transaction. As investors, the same goes for information about firms seeking our funds. This is information that sellers and fund-seeking firms typically have. But, when it is too difficult or too costly to collect information, markets function poorly or not at all.

Economists use the term adverse selection to describe the problem of distinguishing a good feature from a bad feature when one party to a transaction has more information than the other party. The degree of adverse selection depends on how costly it is for the uninformed actor to observe the hidden attributes of a product or counterparty. When key characteristics are sufficiently expensive to discern, adverse selection can make an otherwise healthy market disappear.

In this primer, we examine three examples of adverse selection: (1) used cars; (2) health insurance; and (3) private finance. We use these examples to highlight mechanisms for addressing the problem....