Unraveling of Dynamic Sorting

We consider a two-sided, finite-horizon search and matching model with heterogeneous types and complementarity between types. The quality of the pool of potential partners deteriorates as agents who have found mutually agreeable matches exit the market. When search is costless and all agents participate in each matching round, the market performs a sorting function in that high types of agents have multiple chances to match with their peers. However, this sorting function is lost if agents incur an arbitrarily small cost in order to participate in each round. With a sufficiently rich type space, the market unravels as almost all agents rush to participate in the first round and match and exit with anyone they meet.

Delay in Strategic Information Aggregation

We study a model of collective decision making in which agents vote on the decision repeatedly until they agree, with the agents receiving no exogenous new information between two voting rounds but incurring a delay cost. Although preference conflict between the agents makes information aggregation impossible in a single round of voting, in the equilibrium of the repeated voting game agents are increasingly more willing to vote their private information after each disagreement. Information is efficiently aggregated within a finite number of rounds. As delay becomes less costly, agents are less willing to vote their private information, and efficient information aggregation takes longer. Even as the delay cost converges to zero, agents are strictly better off in the repeated voting game than in any single round game for moderate degrees of initial conflict.repeated voting; gradual concessions; small delay cost

The tone production in Cantonese profoundly hearing impaired children and the usefulness of residual hearing at low frequency

Also available in print.A dissertation submitted in partial fulfilment of the requirements for the Bachelor of Science (Speech and Hearing Sciences), University of Hong Kong, Appril 30, 1992.Thesis (B.Sc)--University of Hong Kong, 1992published_or_final_versionSpeech and Hearing SciencesBachelorBachelor of Science in Speech and Hearing Science

First in Village or Second in Rome

Though individuals prefer to join groups with high quality peers, there are also advantages from being high up in the pecking order within the group. We show that sorting of agents in this environment results in an overlapping interval structure in the type space. Segregation and mixing coexist in a stable equilibrium. A greater degree of egalitarianism within organizations leads to greater segregation across organizations. Policies that are effective for lower-quality organizations to attract talent may be counterproductive for higher-quality organizations to retain talent. The degree and the pattern of segregation are shown to depend also on whether higher types are less concerned with relative ranking within the organization, on relative size of organizations, and on the extent of idiosyncratic preferences for other organizational attributes.

Optimal deadlines for agreements

Costly delay in negotiations can induce the negotiating parties to be more forthcoming with their information and improve the quality of the collective decision. Imposing a deadline may result in stalling, in which players at some point stop making concessions but switch back to conceding at the end, or a deadlock, in which concessions end permanently. Extending the deadline hurts the players in the first case but is beneficial in the second. When the initial conflict between the negotiating parties is intermediate, the optimal deadline is positive and finite, and is characterized by the shortest time that would allow efficient information aggregation in equilibrium.Repeated proposals, war of attrition, interdependent values

Credible Ratings

This paper considers a model of a rating agency with multiple clients. ach client has a separate market (end-user of the rating); the only connection among them is that the underlying qualities of the clients are correlated. In the benchmark case of individual rating, the market for each client does not know the ratings for other clients. In centralized rating, the agency rates all clients together and shares the rating information among all markets. In decentralized rating, the ratings are again shared among all markets, but each client is rated by a self-interested rater of the agency with no access to the quality information of other clients. Both centralized rating and decentralized rating weakly dominate individual rating for the agency. When the underlying qualities are weakly correlated, centralized rating can dominate decentralized rating, but the reverse holds when the qualities are strongly correlated.

Credible ratings

This paper considers a model of a rating agency with multiple clients, in which each client has a separate market that forms a belief about the quality of the client after the agency issues a rating. When the clients are rated separately (individual rating), the credibility of a good rating in an inflationary equilibrium of the signaling game is limited by the incentive of the agency to exaggerate the quality of the client. In centralized rating, the agency rates all clients together and shares the rating information among all markets. This allows the agency to coordinate the ratings and achieve a higher average level of credibility for its good ratings than in individual rating. In decentralized rating, the ratings are again shared among all markets, but each client is rated by a self-interested rater of the agency with no access to the quality information of other clients. When the underlying qualities of the clients are correlated, decentralized rating leads to a smaller degree of rating inflation and hence a greater level of credibility than in individual rating. Comparing centralized rating with decentralized rating, we find that centralized rating dominates decentralized rating for the agency when the underlying qualities are weakly correlated, but the reverse holds when the qualities are strongly correlated.Signaling, credibility, individual rating, centralized rating, decentralized rating

A Signaling Theory of Grade Inflation

When employers cannot tell whether a school truly has many good students or just gives easy grades, schools have an incentive to inflate grades to help mediocre students, despite concerns about preserving the value of good grades for good students. We construct a signaling model where grades are inflated in equilibrium. The inability to commit to an honest grading policy reduces the informativeness of grades and hurts schools. Grade inflation by one school makes it easier for another school to fool the market with inflated grades. Easy grades are strategic complements, providing a channel to make grade exaggeration contagious.

Competing for Talents

Though individuals prefer to join groups with high quality peers, there are advantages to being high up in the pecking order within a group if higher ranked members of a group have greater access to the group's resources. When two organizations try to attract members from a ¯xed population of heterogeneous agents, how resources are distributed among the members according to their rank a®ects how agents choose between the organizations. Competition between the two organizations has implications for both the equilibrium sorting of agents and the way resources are distributed within each organization. To compete more intensely for the more talented agents, both organizations are selective and give no resources to their low ranks. In both organizations, higher ranks are rewarded with more resources, with a greater rate of increase in the organization that has a lower average quality in equilibrium.

Credibility of Crime Allegations

The lack of hard evidence in allegations about sexual misconduct makes it difficult to separate true allegations from false ones. We provide a model in which victims and potential libelers face the same costs and benefits from making an allegation, but the tendency for perpetrators of sexual misconduct to engage in repeat offenses allows semiseparation to occur, which lends credibility to such allegations. Our model also explains why reports about sexual misconduct are often delayed, and why the public rationally assigns less credibility to these delayed reports