Interactive modelAdvanced Microadvanced

Adverse Selection (Lemons Problem)

Akerlof's used-car market: how hidden quality can unravel a market entirely.

Equilibrium: q* = 33.3, P* = 40.0

Current equations

Buyers' willingness to pay: P = 20 + 0.6·qPrice good-car owners need: P = 10 + 0.9·q

Buyers cannot tell good cars from lemons, so they offer a price for the average car. But at an average price, owners of the best cars keep them. Quality on the market falls, buyers offer less, more good cars leave. The crossing shows where the unraveling stops, and it can go all the way to zero.

Shift the curves

Buyer trust (history reports, inspections)0

Anything that verifies quality lets buyers pay more, keeping good cars in the market.

The Adverse Selection (Lemons Problem) model, in writing

Definition

Market failure from hidden characteristics: when quality is private information, prices attract the worst types. Akerlof's market for lemons.

Buyers offer E[quality] price → sellers above that price exit → average quality falls → repeat

The intuition

If buyers will only pay the average-quality price, owners of good cars keep them, the average falls, the price falls further, and the market can unravel to nothing. Insurance faces the mirror image: the sickest are keenest to buy.

Exam tip

The trigger is information asymmetry BEFORE the transaction; hidden behavior AFTER it is moral hazard.

Related models in Advanced Micro

Consumer Theory (Indifference Curves) →Producer Theory (Isoquants & Isocosts) →Cournot Competition →Auction Theory →