Mediated contracts and mechanism design

The framework of incentive compatible finite direct coordination mechanisms in the sense of Myerson (1982) [5] is isomorphic to a framework of incentive compatible stochastic mediated contracts in the sense of Rahman and Obara (2010) [11] and Rahman (2009) [10]. The equivalence follows because the framework of Myerson (1982) [5] allows for a correlation between recommendations and transfers. The literature has hitherto not recognized the importance of this correlation for the structure of optimal contracts and for extending the revelation principle to address agency (moral hazard) problems.     

Hard evidence and mechanism design

This paper addresses how hard evidence can be incorporated into mechanism-design analysis. Two classes of models are compared: (a) ones in which evidentiary decisions are accounted for explicitly, and (b) ones in which the players make abstract declarations of their types. Conditions are provided under which versions of these models are equivalent. The paper also addresses whether dynamic mechanisms are required for Nash implementation in settings with hard evidence. The paper shows that static mechanisms suffice in the setting of “evidentiary normality” and that, in a more general environment, one can restrict attention to a class of three-stage dynamic mechanisms.     

Optimal combinatorial mechanism design

We consider an optimal mechanism design problem with several heterogenous objects and interdependent values. We characterize ex post incentives using an appropriate monotonicity condition and reformulate the problem in such a way that the choice of an allocation rule can be separated from the choice of the payment rule. Central to the analysis is the formulation of a regularity condition, which gives a recipe for the optimal mechanism. If the problem is regular, then an optimal mechanism can be obtained by solving a combinatorial allocation problem in which objects are allocated in a way to maximize the sum of virtual valuations. We identify conditions that imply regularity using the techniques of supermodular optimization.     

Commentary: Nash equilibrium and mechanism design

I argue that the principal theoretical and practical drawbacks of Nash equilibrium as a solution concept are far less troublesome in problems of mechanism design than in most other applications of game theory.     

Seller competition by mechanism design

This paper analyzes a market game in which sellers offer trading mechanisms to buyers and buyers decide which seller to go to depending on the trading mechanisms offered. In a (subgame perfect) equilibrium of this market, sellers hold auctions with an efficient reserve price but charge an entry fee. The entry fee depends on the number of buyers and sellers, the distribution of buyer valuations, and the buyer cost of entering the market. As the size of the market increases, the entry fee decreases and converges to zero in the limit. We study how the surplus of buyers and sellers depends on the number of agents on each side of the market in this decentralized trading environment.     

Endogenous groups and dynamic selection in mechanism design

We create a dynamic theory of endogenous risk sharing groups, with good internal information, and their coexistence with relative performance, individualistic regimes, which are informationally more opaque. Inequality and organizational form are determined simultaneously. Numerical techniques and succinct reformulations of mechanism design problems with suitable choice of promised utilities allow the computation of a stochastic steady state and its transitions. Regions of low inequality and moderate to high wealth (utility promises) produce the relative performance regime, while regions of high inequality and low wealth produce the risk sharing group regime. If there is a cost to prevent coalitions, risk sharing groups emerge at high wealth levels also. Transitions from the relative performance regime to the group regime tend to occur when rewards to observed outputs exacerbate inequality, while transitions from the group regime to the relative performance regime tend to come with a decrease in utility promises. Some regions of inequality and wealth deliver long term persistence of organization form and inequality, while other regions deliver high levels of volatility.     

Correlated information, mechanism design and informational rents

Crémer and McLean (Econometrica 56 (1988) 1247-1258) obtain a sufficient and necessary condition for full surplus extraction in Bayesian-Nash equilibrium—the rank condition, which McAfee and Reny (Econometrica 60(2) (1992) 395-421) later generalize for continuous type spaces. This paper shows that, if the principal does not know how noisy is the agent's signal—or equivalently, when signals available to an agent can be ranked by Blackwell's informativeness and, an agent's informativeness is independent of others’ information, the rank condition fails to hold. Conversely, when rank condition fails and informational rents are left to an agent, the model can be interpreted as if, the principal were uncertain about the informativeness of the agent's signal.     

Dynamic mechanism design with hidden income and hidden actions

We develop general recursive methods to solve for optimal contracts in dynamic principal-agent environments with hidden states and hidden actions. Starting from a general mechanism with arbitrary communication, randomization, full history dependence, and without restrictions on preferences or technology, we show that the optimal contract can be implemented as a recursive direct mechanism. A curse of dimensionality which arises from the interaction of hidden income and hidden actions can be overcome by introducing utility bounds for behavior off the equilibrium path. Environments with multiple actions are implemented using multiple layers of such off-path utility bounds.     

Optimal mechanism design with resale via bargaining

In this paper, we examine the optimal mechanism design of selling an indivisible object to one regular buyer and one publicly known buyer, where inter-buyer resale cannot be prohibited. The resale market is modeled as a stochastic ultimatum bargaining game between the two buyers. We fully characterize an optimal mechanism under general conditions. Surprisingly, in this optimal mechanism, the seller never allocates the object to the regular buyer regardless of his bargaining power in the resale market. The seller sells only to the publicly known buyer, and reveals no additional information to the resale market. The possibility of resale causes the seller to sometimes hold back the object, which under our setup is never optimal if resale is prohibited. We find that the seller?s revenue is increasing in the publicly known buyer?s bargaining power in the resale market. When the publicly known buyer has full bargaining power, Myerson?s optimal revenue is achieved; when the publicly known buyer has no bargaining power, a conditionally efficient mechanism prevails.     

Reciprocal deposits and incremental bank risk

Even after controlling for other observable factors, reciprocal deposits are associated with higher bank risk as measured by the probability of failure and the Z-score. These results are consistent with the moral hazard hypothesis and reject the risk substitution hypothesis.     

Multidimensional mechanism design: Revenue maximization and the multiple-good monopoly

The seller of N distinct objects is uncertain about the buyer's valuation for those objects. The seller's problem, to maximize expected revenue, consists of maximizing a linear functional over a convex set of mechanisms. A solution to the seller's problem can always be found in an extreme point of the feasible set. We identify the relevant extreme points and faces of the feasible set. We provide a simple algebraic procedure to determine whether a mechanism is an extreme point. We characterize the mechanisms that maximize revenue for some well-behaved distribution of buyer's valuations.     

Regular type distributions in mechanism design and \rho -concavity

Some of the best-known results in mechanism design depend critically on Myerson’s (Math Oper Res 6:58–73, 1981) regularity condition. For example, the second-price auction with reserve price is revenue maximizing only if the type distribution is regular. This paper offers two main findings. First, a new interpretation of regularity is developed—similar to that of a monotone hazard rate—in terms of being the next to fail. Second, using expanded concepts of concavity, a tight sufficient condition is obtained for a density to define a regular distribution. New examples of regular distributions are identified. Applications are discussed.     

Reciprocal Supervision,Collusion and Organizational Design

We study the design of supervisory functions in an organization with one principal and two agents. Each agent can perform supervision activities regarding the other agent. We characterize the way the principal must structure incentive payments to avoid any collusive activity between agents. In particular, it is shown that better mutual information between agents may hurt the principal. The other main result is the possibility that it may be better to give up one supervisory function or to have a third party be the supervisor if possible. Finally, we show that such a dual supervisory structure raises the possibility that letting collusion happen may be the best policy.     

The relevance of private information in mechanism design

Recent results in mechanism design show that as long as agents have correlated private information and are sufficiently risk neutral, it is possible to design mechanisms that leave agents with arbitrarily small information rents. We show that these full-rent-extraction results hinge on the implicit assumption that the agents’ beliefs uniquely determine their preferences. We present an example of the voluntary provision of a public good in which this assumption is relaxed, and consequently, even in highly correlated environments, if agents’ beliefs do not uniquely determine their preferences, then the extraction of the agents’ entire information rents is impossible.     

Utilitarian mechanism design for an excludable public good

This paper studies the design of optimal utilitarian mechanisms for an excludable public good. Excludability provides a basis for making people pay for admissions; the payments can be used for redistribution and/or funding. Whereas previous work assumed that admissions are governed by the payment or nonpayment of a price, this paper allows for arbitrary admission rules. With sufficient inequality aversion, nondegenerate randomization in admissions is shown to be desirable for certain model specifications, with and without participation constraints. The paper also gives a sufficient condition on the distribution of preferences under which randomization is undesirable.     

Creating Creditworthiness through Reciprocal Trade

The paper investigates how barter can be used to finance imports and restore the creditworthiness of highly indebted countries when reputation as an enforcement mechanism for credit repayment does not work. The authors argue that payments in goods can be used to collateralize a trade credit and thus improve the creditor's incentives to pursue defaulting debtors. Furthermore, it is shown that barter is particularly advantageous if export revenues of the debtor country are stochastic, even in the absence of risk aversion. The predictions of the model are consistent with data on actual barter contracts.     

Endogenous contest success functions: a mechanism design approach

We describe optimal contest success functions (CSF) which maximize expected revenues of an administrator who allocates under informational asymmetry a source of rent among competing bidders. It is shown that in the case of independent private values rent administrator’s optimal mechanism can always be implemented via some CSFs as posited by Tullock. Optimal endogenous CSFs have properties which are often assumed a priori as plausible features of rent-seeking contests; the paper therefore validates such assumptions for a broad class of contests. Various extensions or optimal CSFs are analyzed.     

The power of randomness in Bayesian optimal mechanism design

We investigate the power of randomness in the context of a fundamental Bayesian optimal mechanism design problem—a single seller aims to maximize expected revenue by allocating multiple kinds of resources to “unit-demand” agents with preferences drawn from a known distribution. When the agents' preferences are single-dimensional Myerson's seminal work (1981) shows that randomness offers no benefit—the optimal mechanism is always deterministic. In the multi-dimensional case, when agents' preferences are arbitrarily correlated, Briest et al. (2010) showed that the gap between the expected revenue obtained by an optimal randomized mechanism and an optimal deterministic mechanism can be unbounded even when a single agent is offered only 4 services. We show that when the agents' values involve no correlation or a specific kind of positive correlation, the benefit of randomness is only a small constant factor.     

The cost of inflation: A mechanism design approach

I apply mechanism design to quantify the cost of inflation that can be attributed to monetary frictions alone. In an environment with pairwise meetings, the money demand that is consistent with an optimal, incentive feasible allocation takes the form of a continuous correspondence that can fit the data over the period 1900–2006. For such parameterizations, the cost of moderate inflation is zero. This result is robust to the introduction of match-specific heterogeneity and endogenous participation decisions.     

Truthful mechanism design for multidimensional scheduling via cycle monotonicity

We consider the makespan-minimization problem on unrelated machines in the context of algorithmic mechanism design. No truthful mechanisms with non-trivial approximation guarantees are known for this multidimensional domain. We study a well-motivated special case (also a multidimensional domain), where the processing time of a job on each machine is either “low” or “high.” We give a general technique to convert any c-approximation algorithm (in a black-box fashion) to a 3c-approximation truthful-in-expectation mechanism. Our construction uses fractional truthful mechanisms as a building block, and builds upon a technique of Lavi and Swamy [Lavi, R., Swamy, C., 2005. Truthful and near-optimal mechanism design via linear programming. In: Proc. 46th FOCS, pp. 595–604]. When all jobs have identical low and high values, we devise a deterministic 2-approximation truthful mechanism. The chief novelty of our results is that we do not utilize explicit price definitions to prove truthfulness. Instead we design algorithms that satisfy cycle monotonicity [Rochet, J., 1987. A necessary and sufficient condition for rationalizability in a quasilinear context. J. Math. Econ. 16, 191–200], a necessary and sufficient condition for truthfulness in multidimensional settings; this is the first work that leverages this characterization.