1. L25 Asymmetric Information

2. Structure of the course 1) Consumers choice 2) Equilibrium, Producers (Pareto efficiency) 3) Market Failures - fixed cost: monopoly and oligopoly - externalities and public goods - asymmetric information

3. Asymmetric Information u Assumption: full information about the traded commodities u What about following markets? 1.Medical services: a doctor knows more than does a patient. 2.Insurance: a buyer knows more about his riskiness than does the seller. 3.Used cars: a car’s owner knows more about it than does a potential buyer u Problem: asymmetric information

4. Today u Q: how does asymmetric information affect the functioning of a market? u Important phenomena  adverse selection (hidden information)  signaling  moral hazard (hidden action)

5. Market for “lemons” u Market for used cars (Akerlof 1970) u Types of cars: “lemons” and “plums”. u Proportion: 50% - 50% u TPS (Total Potential Surplus) LemonPlum Seller10002000 Buyer12002400

6. Benchmark: perfect information u Prices (halfway): u Buyer’s and seller’s surplus u TPS and BS+SS? LemonPlum Seller10002000 Buyer12002400

7. Asymmetric information u Asymmetric information (50% - 50%) u TPS and BS, SS u Separating Equilibrium LemonPlum Seller10002000 Buyer12002400

8. Separating equilibrium u Asymmetric information (, ) LemonPlum Seller10002000 Buyer12002400

9. Pooling equilibrium u Asymmetric information (, ) u Efficient outcome LemonPlum Seller10002000 Buyer12002400

10. Adverse Selection Separating equilibrium u Lemons “crowd out” plums from the market. u Surplus is reduced since no plums are traded u Very bad for plum owners Pooling equilibrium u Lemon owners “hide behind” the plums u Somewhat bad for plum owners u Pareto efficiency (full surplus) Probability of “bad type” is high: compulsory insurance

11. Signaling u Asymmetric information bad for “good” types u Incentive: Credible signal of high-quality u Examples of signals: warranties, professional credentials, references from previous clients, costly adds, education etc.

12. Signaling (in Labor Market) u Two types of managers - high-ability manager has productivity (a plum) - low-ability manager has productivity (a lemon) u Fraction of high-productivity managers u Competitive markets u Benchmark: No signal (pooling)

13. Equilibrium with signaling Signal: MBA education u Years of education Cost of education (MBA) u For high-ability worker education costless u For low-ability worker Benefit of education u MBA has no effect on workers’ productivities u Talent not observed but MBA diploma yes - signal u Q: Is there a separating equilibrium with signaling?

14. (Non) Credible signal u Is MBA a credible signal with e=2? u Suppose

15. Credible signal u Credibility condition

16. A credible signal u Can we separate now? u Same credibility condition u Deadweight loss (burning money) u Common in real world: adds

17. Moral Hazard (hidden action) u With full car insurance are you more likely to leave your car unlocked? u With fixed hourly wage is your effort at work reduced? u Moral hazard is a reaction to incentives to increase the risk of a loss u A consequence of asymmetric information (hidden action).

18. Moral hazard u Perfect information: full insurance u Asymmetric information: -partial insurance -contract that depends on output To induce proper incentives