主 题：Directed Search
主讲人：Peter Norman
主持人： 金融学院 李四光老师
时 间：2015年12月1日至12月4日每天下午13:30 – 16:30
地 点：格致楼411会议室
主办单位：金融学院 、科研处
主讲人简介：
Professor Peter Norman
University of Pennsylvania, Ph.D. in Economics, August 1997.
Professor, University of North Carolina at Chapel Hill, July 2010-present.
Associate Professor, University of North Carolina at Chapel Hill, July 2007-2010.
Associate Professor, University of British Columbia, August 2004-June 2007.
Assistant Professor, University of Wisconsin-Madison, September 1997-July 2004.
Peter Norman在学术界有较强影响力，在国际杂志American Economic Review, Review of Economic Studies, Rand Journal of Economics, Journal of Economic Theory, International Economic Review发表了一系例文章。
内容提要：
Much recent applied work in industrial organization, labor and macroeconomics uses models with search frictions. Most such models, called random search models, postulates a matching function, which may be simple urn-ball matching or something more elaborate. In directed search on the other hand, the matching function is an object determined in equilibrium. The key idea is that is that even if contracts are posted for all agents to observe and agents can decide which principal to visit there may still be more agents visiting a particular principal than that principal can serve in equilibrium. Hence, there will be rationing in equilibrium, which creates an endogenous friction and an associated equilibrium matching function.
There are two basic approaches to directed search. The most solidly micro-founded version assumes a finite set of agents on each side of the market. We will consider such a setup for the canonical case with n buyers and m capacity constrained sellers. An alternative, often more tractable, version assumes a continuum of agents. Obviously, an important question is when the continuum model can be seen as an approximation of exact equilibria in the finite case. We will establish that this is the case in the simple example with identical buyers and sellers, but the answer is still an open question for many more complex applications.
The standard approach in directed search is to restrict attention to symmetric mixed strategy equilibria. There is a plethora of other equilibria, and, in some cases, such as the buyer-seller model with equal numbers of buyers and sellers, there are even equilibria where the frictions disappear altogether. Usually such equilibria are ignored, sometimes with the justification that coordination is di￠ cult in large markets. We will consider a version of the model in which this problem disappears. In the case with buyers and sellers, the model is identical to the standard setup except that the number of buyers is a Poisson random variable with mean n and the number of sellers is a Poisson random variable with mean m: In this model coordination equilibria disappear (even if agents are given labels to coordinate.
