Archive · 5 Oct 2026
Why Screening and Signalling Matter in Markets With Unequal Information
Sometimes one person knows more about something being bought or sold than the other person.
A used-car seller may know whether a car is good or bad, but a buyer may not.
If buyers cannot tell the difference, they may offer low prices, and sellers of good cars may leave.
That can leave more poor-quality cars for sale.
Similar information problems can happen with insurance and loans.
Stiglitz suggested screening, which means asking questions or using choices to learn more about someone.
Spence suggested signalling, which means showing something that helps prove you are trustworthy or capable.
The article says these ideas still matter, especially when information is noisy or hard to judge.
The article marks the 25th anniversary of the 2001 Economics Nobel awarded to George Akerlof, Michael Spence and Joseph Stiglitz for work on markets with asymmetric information.
Akerlof’s “lemons” model shows how buyers’ uncertainty about quality can drive good used cars, or “peaches,” out of the market.
The article describes adverse selection in markets including used cars, medical insurance and credit, where unequal information can leave markets with lower-quality products or riskier participants.
Stiglitz proposed screening, while Spence emphasized signalling, as ways to help parties reveal or assess information they do not initially have.
The article says guarantees, brands, contracts and other market institutions can help address information problems, which digital technology and social media have made more complex.
- Who
- Economists George Akerlof, Michael Spence and Joseph Stiglitz, whose work is discussed by Amol Agrawal.
- What
- An explanation of information asymmetry, adverse selection, screening and signalling in markets.
- When
- The article marks the 25th anniversary of the 2001 Economics Nobel Prize.
- Where
- The discussion covers markets including used cars, medical insurance and credit, and refers to Akerlof’s work in India.
- Why
- Unequal or unclear information can distort markets; screening, signalling and market institutions can help address the problem.
- Nobel anniversary
- 2026 marks 25 years since the 2001 Economics Nobel Prize.
- Nobel recipients discussed
- George Akerlof, Michael Spence and Joseph Stiglitz.
- Akerlof’s model
- His 1970 article, “The Market for ‘Lemons’: Quality Uncertainty and the Market Mechanism,” examines quality uncertainty.
- Adverse selection
- A problem arising when one party has more information, potentially driving better-quality products or lower-risk participants from a market.
- Stiglitz’s approach
- Screening can help insurers or other parties learn about the people they deal with.
- Spence’s approach
- Signalling uses observable actions, such as education qualifications, to indicate credibility or quality.
- Other mechanisms
- The article names guarantees, brands, chain stores, franchising and contracts as responses to information problems.