We suggest an architecture for executing protocols for auctions and, more generally, mechanism design. Our goal is to preserve the privacy of the inputs of the participants (so that no nonessential information about them is divulged, even a posteriori) while maintaining communication and computational efficiency. We achieve this goal by adding another party - the auction issuer - that generates the programs for computing the auctions but does not take an active part in the protocol. The auction issuer is not a trusted party, but is assumed not to collude with the auctioneer. In the case of auctions, barring collusion between the auctioneer and the auction issuer, neither party gains any information about the bids, even after the auction is over. Moreover, bidders can verify that the auction was performed correctly. The protocols do not require any communication between the bidders and the auction issuer and the computational efficiency is very reasonable. This architecture can be used to implement any mechanism design where the important factor is the complexity of the decision procedure.

Abstract We study a class of single round, sealed bid auctions for items in unlimited supply such as digital goods. We focus on auctions that are truthful and competitive. Truthful auctions encourage bidders to bid their utility; competitive auctions yield revenue within a constant factor of the revenue for optimal fixed pricing. We show that for any truthful auction, even a multi-price auction, the expected revenue does not exceed that for optimal fixed pricing. We also give a bound on how far the revenue for optimal fixed pricing can be from the total market utility. We show that several randomized auctions are truthful and competitive under certain assumptions, and that no truthful deterministic auction is competitive. We present simulation results which confirm that our auctions compare favorably to fixed pricing. Some of our results extend to bounded supply markets, for which we also get truthful and competitive auctions.

A benchmark "package auction" is introduced in which bidders may determine their own packages on which to bid. If all bidders bid straightforwardly, then the outcome is a point in the core of the exchange economy that minimizes the seller's revenue. When goods are substitutes, straightforward bidding strategies comprise an ex post Nash equilibrium. Compared to the Vickrey auction, the benchmark ascending package auction has cheaper information processing, better handling of budget constraints, and less vulnerability to joint bidding strategies among bidders who would otherwise be losers. Improvements are suggested that speed the auction and limit opportunities for collusion.

This paper describes the auction rules and how bidders prepared for the auction. The full history of bidding is presented. Several questions for auction theory are discussed. In the end, the government collected $617 million for ten licenses. The auction was viewed by all as a huge success---an excellent example of bringing economic theory to bear on practical problems of allocating scarce resources.

. This paper develops an evolutionary trade network game (TNG) that combines evolutionary game play with endogenous partner selection. Successive generations of resource-constrained buyers and sellers choose and refuse trade partners on the basis of continually updated expected payoffs. Trade partner selection takes place in accordance with a modified Gale-Shapley matching mechanism, and trades are implemented using trade strategies evolved via a standardly specified genetic algorithm. The trade partnerships resulting from the matching mechanism are shown to be core stable and Pareto optimal in each successive trade cycle. Nevertheless, computer experiments suggest that these static optimality properties may be inadequate measures of optimality from an evolutionary perspective. 1 Introduction Evolutionary game studies typically focus on the optimality properties of strategy configurations when agents are matched randomly or deterministically by some extraneous device. The optimality p...

This paper introduces a new model of exchange: networks, rather than markets, of buyers and sellers. It begins with the empirically motivated premise that a buyer and seller must have a relationship, a “link, ” to exchange goods. Networks- buyers, sellers, and the pattern of links connecting them- are common exchange environments. This paper develops a methodology to study network structures and explains why agents may form networks. In a model that captures characteristics of a variety of industries, the paper shows that buyers and sellers, acting strategically in their own self-interests, can form the network structures that maximize overall

We create an environment in which congestion forces agents to match inefficiently early. We then introduce one of two centralized clearinghouse mechanisms. One of these has been successfully used to halt this kind of unraveling in a number of labor markets, while the other has failed. When it is costly for �rms and workers to be mismatched compared with the costs of matching early, the experimental observations reproduce the �eld observations. Furthermore, the experiment permits us to observe the transition between a decentralized and a centralized market, both when the centralized market fails to control unraveling and when it succeeds, at a level of detail unavailable in �eld data. Field studies of competitive entry-level professional labor markets reveal a common form of market failure involving the ‘‘unraveling’ ’ of hiring decisions, in which employment contracts from year to year become earlier and earlier in advance of employment, even when this becomes very costly {Roth and Xing 1994}. Sometimes the cause is that the market is organized in

The entry-level market for American gastroenterologists was organized by a centralized clearinghouse from 1986 to 1996. Before, and since, it has been conducted via a decentralized market in which appointment dates have unraveled to well over a year before the start of employment. We find that, both before and after the years in which the centralized clearinghouse was used, gastroenterologists are less mobile and more likely to be employed at the same hospital in which they were internal medicine residents than when the clearinghouse was in use. This suggests that the clearinghouse not only coordinates the timing of appointments but also increases the scope of the market, compared to a decentralized market with early appointments.

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This paper studies the assignment of heterogeneous workers to heterogeneous jobs in the presence of coordination frictions. Firms o#er human-capital-contingent wages, workers observe these and apply for a job. In a symmetric equilibrium, identical workers use identical mixed strategies in deciding where to apply, and the randomness introduced by mixed strategies generates equilibrium unemployment and vacancies. The equilibrium can be interpreted as the competitive equilibrium of a closely related model, ensuring constrained e#ciency. The model generates a rich interaction between the heterogeneous workers and firms. Firms attract applications from multiple types of workers, and earn higher profits when they hire a more productive worker. Identical workers apply for jobs with di#erent productivity and get higher wages when they land a more productive job. Despite this mismatch, I show that in some special cases, the model generates assortative matching, with a positive correlation between matched workers' and firms' productivity. # I am grateful to Jaap Abbring, Daron Acemoglu, James Heckman, Ian King, Shouyong Shi, and Chris Sims for useful discussions. I have also benefited from comments by many seminar participants at the NBER Summer Institute 2001, the Minnesota Workshop in Macro Theory, and Princeton. I thank the University of Chicago for its hospitality in April and May 2001 while I wrote the first draft of this paper, the National Science Foundation for financial support, and Sebastian Ludmer for excellent research assistance. 1