Incentives of low‐quality sellers to disclose negative information

The paper studies incentives of low‐quality sellers to disclose negative information about their products. We develop a model in which one's quality can be communicated via cheap‐talk messages only. This setting limits the ability of high‐quality sellers to separate, as any communication strategy they pursue can be costlessly imitated by low‐quality sellers. We study two factors that can incentivize low‐quality sellers to communicate their quality: buyers' loss aversion and competition. Quality disclosure reduces buyers' risk, thereby increasing their willingness to pay for the product. It also introduces product differentiation, softening the competition.     

Dominance solvability of second-price auctions with differential information

We study a class of common-value second-price auctions with differential and finite information. This class is characterized by the property that each bidder’s information set is connected with respect to the common value. We show that the entire class is dominance solvable, and that there is a natural single-valued selection from the resulting set of sophisticated equilibria. Additionally, it is shown that bidder’s information advantage over other bidders is rewarded in sophisticated equilibria.     

Efficiency and information aggregation in auctions with costly information

Consider an auction in which k identical objects are sold to n > k bidders who each have a value for one object which can have both private and common components to it. Private information concerning the common component of the object is not exogenously given, but rather endogenous and bidders face a cost to becoming informed. If the cost of information is not prohibitively high, then the equilibrium price in a uniform price auction will not aggregate private information, in contrast to the costless information case. Moreover, for a wide class of auctions if the cost of information is not prohibitively high then the objects can only be allocated in a weakly efficient sense, and then only if the equilibrium proportion of endogenously informed agents is vanishing as the economy grows. In spite of these results, it is shown that there is a mechanism for which there exist equilibria and for which (weak) efficiency is achieved as the economy grows in the face of endogenous information acquisition.Received: 6 August 2001, Accepted: 27 July 2002, JEL Classification: C72, D44, D82Financial support under NSF grant SBR-9507912 is gratefully acknowledged. I thank Valentina Bali for conversations out of which this project grew, and Larry Ausubel for a very helpful discussion of an early version of this paper at the 1998 summer meetings of the Econometric Society from which I have borrowed in structuring the exposition of the paper. I also thank Andy Postlewaite, Jeroen Swinkels, and an associate editor and anonymous referee for helpful comments and suggestions on earlier drafts.     

On the convergence of genetic learning in a double auction market

We study the learning behavior of a population of buyers and a population of sellers whose members are repeatedly randomly matched to engage in a sealed bid double auction. The agents are assumed to be boundedly rational and choose their strategies by imitating successful behavior and adding innovations triggered by random errors or communication with other agents. This process is modelled by a two-population genetic algorithm. A general characterization of the equilibria in mixed population distributions is given and it is shown analytically that only one price equilibria are attractive for the GA dynamics. Simulation results confirm these findings and imply that in cases with random initialization with high probability the gain of trade is equally split between buyers and sellers.     

Reputation in Auctions: Theory, and Evidence from eBay

Employing a procedure suggested by a simple theoretical model of auctions in which bidders and sellers have observable and heterogenous reputations for default, we examine the effect of reputation on price in a data set drawn from the online auction site eBay. Our main empirical result is that seller's, but not bidder's, reputation has an economically and statistically significant effect on price.     

Second‐Price Auctions with Different Participation Costs

This paper studies equilibria of second‐price auctions in independent private value environments with different participation costs. Two types of equilibria are identified: monotonic equilibria in which a bidder with a lower participation cost results in a lower cutoff for submitting a bid, and nonmonotonic equilibria in which a lower participation cost results in a higher cutoff. We show that there always exists a monotonic equilibrium, and further, that the monotonic equilibrium is unique for either concave distribution functions or strictly convex distribution functions with nonincreasing reverse hazard rates. There exist nonmonotonic equilibria when the distribution functions are strictly convex and the difference of the participation costs is sufficiently small. We also provide comparative static analysis and study the limiting properties of equilibria when the difference in bidders’ participation costs approaches zero.     

Communication equilibria with partially verifiable types

This paper studies the set of equilibria that can be achieved by adding general communication systems to Bayesian games in which some information can be certified or, equivalently, in which players’ types are partially verifiable. Certifiability of information is formalized by a set of available reports for each player that varies with the true state of the world. Given these state-dependent sets of reports, we characterize canonical equilibria for which generalized versions of the revelation principle are valid. Communication equilibria and associated canonical representations are obtained as special cases when no information can be certified.     

On sellers' cooperation in hybrid marketplaces

Hybrid marketplaces, such as Amazon's and Zalando's stores or Apple's and Google's app stores, which distribute their own products and services in competition with those of third-party sellers, play a significant and growing role in the Internet economy. This paper shows that, other things equal, such platforms would maximize their profits if they lowered the fees charged to sellers and the prices charged to consumers in response to cooperation agreements between third-party sellers: horizontal mergers or collusive agreements. It also shows that such cooperation can be pro-competitive when the platform is a vertically integrated gatekeeper, adopts the agency business model, is a close competitor to the third-party sellers it hosts, and observes (or correctly anticipates) the third-party sellers' agreement. The discussion here is of significant policy relevance, since third-party sellers in online marketplaces may find it easier to collude and may respond to the bargaining power of certain gatekeeper platforms by merging their activities.     

The expert problem: a survey

The survey is focused on the typical problems in information transmission from experts to non-experts. Attention is paid to the factors that can affect information disclosure in models that apply a game-theoretic approach to the use of professional advice. In the economic literature expertise is mainly analyzed as a special case of asymmetric information between expert and non-expert. The contributions are reviewed according to a double criterion, that takes into account both the preferences of the experts and the properties of communication. On one side, either the non-expert plays the role of a decision-maker, who chooses an action that is payoff-relevant for the expert, or the preferences of the expert directly depend on some measure of his reputation as a high-ability forecaster. On the other side, communication can range from pure cheap talk to completely verifiable messages.     

Information precision and asymptotic efficiency of industrial markets

I present a strategic model of a bilateral oligopoly with asymmetric information to examine (i) the validity of the conjecture of price-taking behavior in such markets as the number of agents becomes large and (ii) the effect of the rate that individual information precision decreases with increased number of agents on convergence to price-taking and efficiency. I show that with downstream competition, increasing the number of sellers may make all participants price-takers in the limit, but increasing the number of buyers may not. When the total precision of information in the market is high, price-taking and full social efficiency is achieved in the limit with large numbers of buyers and sellers. However, if the total precision of information in the market is poor, price-taking conjecture may fail and large inefficiencies, including full inefficiency, can occur in the limiting outcome. The rate of decrease of individual information precision with increased number of agents determines the rate of convergence to efficiency, and the convergence is slower than that predicted by single-unit auction models in the literature. I also demonstrate that when the number of sellers or both the number of buyers and the sellers go to infinity, price-taking and information aggregation tend to go together. When the number of buyers goes to infinity, however, information can get aggregated when the agents do not become price-takers in the limit. Albeit, in the latter case, the aggregated information is masked by the noise in the sellers’ signals and the cost variability.     

Advertising as Information: Matching Products to Buyers

We consider communication of quality via cheap talk and dissipative advertising expenditures, when consumers have heterogeneous tastes for quality, and price information must be acquired through costly search. For search pods, cheap talk communicates quality when fixed costs are roughly constant across quality levels, while if fixed costs vary greatly with quality, then firms having the higher fixed-cost quality level use dissipative advertising. For experience goods, quality can be communicated by cheap talk in a range where low-quality firms have greater fixed costs, and low-quality firms use dissipative advertising if their fixed costs are greater still.     

Competition among mechanism designers in a common value environment

A competitive economy is studied in which sellers offer alternative direct mechanisms to buyers who have private information about their own private use value for the commodity being traded. In addition the commodity has a common value to all buyers, perhaps represented by the future resale value of the commodity. A competitive equilibrium in mechanisms is described. In every such equilibrium it is shown that sellers must offer mechanisms that are allocationally equivalent to English ascending price auctions. The reservation prices that sellers set are shown to be below their ex post cost of trading the commodity. Received: 24 April 1998 / Accepted: 8 March 1999     

Core and competitive equilibria: An approach from discrete convex analysis

We extend the assignment market (Shapley and Shubik, 1972; Kaneko, 1976, 1982) by utilizing discrete convex analysis. We consider the market in which buyers and sellers trade indivisible commodities for money. Each buyer demands at most one unit of commodity. Each seller produces multiple units of several types of commodities. We make the quasi-linearity assumption on the sellers, but not on the buyers. We assume that the cost function of each seller is M^♮-convex, which is a concept in discrete convex analysis. We prove that the core and the competitive equilibria exist and coincide in our market model.     

Organizations and overlapping generations games: Memory,communication, and altruism

This paper studies the role of memory and communication in overlapping generations (OLG) games between ongoing organizations. In each organization, each individual, upon entry into the game, replaces his predecessor who has the same preferences and faces the same strategic possibilities. An individual has no prior memory - that is, he does not directly witness the events that occur before his tenure. Instead, each individual relies on information about the past from his predecessor via cheap talk. This paper highlights the role of communication as a surrogate for memory.It has been shown elsewhere that Folk Theorems hold in OLG games with long enough lived individuals who can perfectly observe the past. However, the Folk Theorem fails for many games when individuals have no prior memory. We show that for OLG games without prior memory but with costly communication, a Folk Theorem holds only when there is some altruistic link between cohorts in an organization. Our main result asserts that if communication costs are sufficiently small, or if altruistic weights on successors are sufficiently large, then a strongly stationary Folk Theorem (i.e., equilibrium payoffs are time invariant) obtains if a managers message is public information. The equilibria in this Folk Theorem require a special form of intergenerational sanctions. In these sanctions, punishment is sometimes carried out long after both victim and perpetrator have left the game. Without this special structure, altruism may in fact destroy cooperation when it would otherwise be possible.Received: 18 April 2003, Accepted: 20 October 2003, JEL Classification: C72, C73, D74, D82We have benefitted from helpful comments and conversations with Luca Anderlini, Kirk Bailey, Hans Haller, Matthew Jackson, and Takashi Shimizu, and numerous seminar participants. This research is partially supported by the National Science Foundation, and by grants-in-aid for scientific research of the Ministry of Education of Japan. Of course, any remaining error is our own.     

Non-existence of equilibrium in Vickrey, second-price, and English auctions

A simple example shows that equilibria can fail to exist in second price (Vickrey) and English auctions when there are both common and private components to bidders’ valuations and private information is held on both dimensions. The example shows that equilibrium only exists in the extremes of pure private and pure common values, and that existence in standard models is not robust to a slight perturbation.     

Keyword auctions with budget-constrained bidders

We study a keyword auction model where bidders have constrained budgets. In the absence of budget constraints, Edelman et al. (Am Econ Rev 97(1):242–259, 2007) and Varian (Int J Ind Organ 25(6):1163–1178, 2007) analyze “locally envy-free equilibrium” or “symmetric Nash equilibrium” bidding strategies in generalized second-price auctions. However, bidders often have to set their daily budgets when they participate in an auction; once a bidder’s payment reaches his budget, he drops out of the auction. This raises an important strategic issue that has been overlooked in the previous literature: Bidders may change their bids to inflict higher prices on their competitors because under generalized second-price, the per-click price paid by a bidder is the next highest bid. We provide budget thresholds under which equilibria analyzed in Edelman et al. (Am Econ Rev 97(1):242–259, 2007) and Varian (Int J Ind Organ 25(6):1163–1178, 2007) are sustained as “equilibria with budget constraints” in our setting. We then consider a simple environment with one position and two bidders and show that a search engine’s revenue with budget constraints may be larger than its revenue without budget constraints.     

The Effect of Organizational form on Information Flow and Decision Quality: Informational Cascades in Group Decision Making

This paper identifies a disadvantage to decision making in a team. We show that in some cases available information is lost due to sequential communication that results in informational cascades. Although incentive contracts exist that prevent cascades, in some cases these contracts do not maximize shareholders' expected residual value and cascades are tolerated in equilibrium. Cascades never occur in hierarchies that exogenously prevent communication. However, when the firm is organized as a hierarchy (and the agents are given the optimal hierarchical contract), in some cases agents will collude and sequentially communicate, admitting the possibility of cascades. In these cases, the principals must monitor and enforce the hierarchical process. When monitoring costs exceed the cost of cascades, the team is the optimal organizational form.     

On axiomatizations of the Shapley value for assignment games

We consider the problem of axiomatizing the Shapley value on the class of assignment games. It turns out that several axiomatizations of the Shapley value on the class of all TU-games do not characterize this solution on the class of assignment games. However, when considering an assignment game as a (communication) graph game where the game is simply the assignment game and the graph is a corresponding bipartite graph where buyers (sellers) are connected with sellers (buyers) only, we show that Myerson’s component efficiency and fairness axioms do characterize the Shapley value on the class of assignment games. Moreover, these two axioms have a natural interpretation for assignment games. Component efficiency yields submarket efficiency stating that the sum of the payoffs of all players in a submarket equals the worth of that submarket, where a submarket is a set of buyers and sellers such that all buyers in this set have zero valuation for the goods offered by the sellers outside the set, and all buyers outside the set have zero valuations for the goods offered by sellers inside the set. Fairness of the graph game solution boils down to valuation fairness stating that only changing the valuation of one particular buyer for the good offered by a particular seller changes the payoffs of this buyer and seller by the same amount.     

Learning through Simultaneous Play: Evidence from Penny Auctions

This paper contributes to the emerging empirical literature on penny auctions, a particular type of all‐pay auctions. We focus on the potential learning effects that bidders may experience over time but also (and particularly) across auctions as a result of their auction participation. Using detailed bid‐level information, we find that, similarly to earlier literature, bidders suffer from a sunk cost fallacy, whereby their probability of dropping out of an auction is decreasing in the number of bids they have already placed in that auction. Although we do find that learning through repeated participation alleviates the sunk cost fallacy, participation in simultaneous penny auctions emerges as a much more effective learning mechanism, ultimately contributing toward bidders earning higher individual surpluses.     

Endogenous information revelation in a competitive credit market and credit crunch

In this paper, we propose a new mechanism able to explain the occurrence of credit crunches. Considering a credit market with an asymmetry of information between borrowers and lenders, we assume that borrowers have to pay a cost to reveal information on the quality of their project. They decide to be transparent if it is necessary for getting a loan or for paying a lower interest rate. Two types of competitive equilibria may exist: an opaque equilibrium in which all projects receive funding without revealing information; a transparent one in which only the best projects reveal information and receive funding. It is also possible to get multiple equilibria. Incorporating this microeconomic mechanism in an OLG model, the economy may experience fluctuations due to the change of regime, and indeterminacy may occur.