We study a two-sided matching market with a set of heterogeneous firms and workers in an environment where jobs are secured by regulation. Without job security Kelso and Crawford have shown that stable outcomes and efficiency prevail when all workers are gross substitutes to each firm. It turns out that by introducing job security, stability and efficiency may still prevail, and even for a significantly broader class of production functions.

]]>A new approach to moral hazard is presented. Once local incentive compatibility is satisfied, the problem of verifying global incentive compatibility is shown to be isomorphic to the problem of comparing two classes of distribution functions. Thus, tools from choice under uncertainty can be brought to bear on the problem. The approach allows classic justifications of the first-order approach (FOA) to be proven using the same unifying methodology. However, the approach is especially useful for analyzing higher-dimensional moral hazard problems. New and more tractable multi-signal justifications of the FOA are derived and implications for optimal monitoring are examined. The approach yields justifications of the FOA in certain settings where the action is multidimensional, as in the case when the agent is multitasking. Finally, a tractable multitasking model with richer predictions than the popular but simple linear-exponential-normal model is presented.

]]>I study the canonical private value auction model for a single good without the quasilinearity restriction. I assume only that bidders are risk averse and the indivisible good for sale is a normal good. I show that removing quasilinearity leads to qualitatively different solutions to the auction design problem. Expected revenue is no longer maximized using standard auctions that allocate the good to the highest bidder. Instead, the auctioneer better exploits bidder preferences by using a mechanism that allocates the good to one of many different bidders, each with strictly positive probability. I introduce a probability demand mechanism that treats probabilities of winning the indivisible good like a divisible good in net supply 1. With enough bidders, it has greater expected revenues than any standard auction, and under complete information, it implements a Pareto efficient allocation.

]]>This paper studies the existence of equilibrium solution concepts in a large class of economic models with discontinuous payoff functions. The issue is well understood for Nash equilibria, thanks to Reny's better-reply security condition (Reny, 1999) and its recent improvements (Barelli and Meneghel, 2013, McLennan et al.., 2011, Reny 2009, 2011). We propose new approaches, related to Reny's work, and obtain tight conditions for the existence of approximate equilibria and of sharing rule solutions in pure and mixed strategies (Simon and Zame, 1990). As byproducts, we prove that many auction games with correlated types admit an approximate equilibrium, and that many competition models have a sharing rule solution.

]]>This paper generalizes a conceptual insight in dynamic contracting with quasilinear payoffs: the principal does not need to pay any information rents for extracting the agent's “new” private information obtained after signing the contract. This is shown in a general model in which the agent's type stochastically evolves over time, and her payoff (which is linear in transfers) depends on the entire history of private and any contractible information, contractible decisions, and her hidden actions. The contract is offered by the principal in the presence of initial informational asymmetry. The model can be transformed into an equivalent one where the agent's subsequent information is independent in each period (type orthogonalization). We show that for any fixed decision–action rule implemented by a mechanism, the agent's rents (as well as the principal's maximal revenue) are the same *as if* the principal could observe and contract on the agent's orthogonalized types after the initial period. We also show that any monotonic decision–action rule can be implemented in a Markovian environment satisfying certain regularity conditions, and we provide a simple “recipe” for solving such dynamic contracting problems.

We consider consumer entry in the canonical monopolistic nonlinear pricing model (Mussa and Rosen 1978) wherein consumers learn their preference “types” after incurring privately known entry costs. We show that by taking into account consumer entry, the nature of optimal nonlinear pricing contracts changes significantly: compared to the benchmark without costly entry, in our model both quality distortion and market exclusion are reduced, sorting is more likely, and whenever bunching occurs, the bunching interval is necessarily smaller. Additionally, under certain conditions the monopoly solution may even achieve the first best (i.e., production efficiency). We also demonstrate that the optimal monopoly solutions can be ranked according to inverse hazard rate functions of the entry cost, which suggests an interesting dynamic for monopolistic nonlinear pricing with consumer entry.

]]>When an agent's motivation is sensitive to how his supervisor thinks about the agent's competence, the supervisor has to take into account both informational and expressive contents of her message to the agent. This paper shows that the supervisor can credibly express her trust in the agent's ability only by being unclear about what to do. Suggesting what to do, i.e., “directives,” could reveal the supervisor's “distrust” and reduce the agent's equilibrium effort level even though it provides useful information about the decision environment. There is also an equilibrium in which directives are neutral in expressive content. However, it is shown that neologism proofness favors equilibria in which directives are double-edged swords.

]]>We study the possibilities for agenda manipulation under strategic voting for two prominent sequential voting procedures: the amendment procedure and the successive procedure. We show that a well known result for tournaments, namely that the successive procedure is (weakly) more manipulable than the amendment procedure at any given preference profile, extends to arbitrary majority quotas. Moreover, our characterizations of the attainable outcomes for arbitrary quotas allow us to compare the possibilities for manipulation across different quotas. It turns out that the simple majority quota maximizes the domain of preference profiles for which neither procedure is manipulable, but at the same time neither the simple majority quota nor any other quota uniformly minimizes the scope of manipulation once this becomes possible. Hence, quite surprisingly, simple majority voting is not necessarily the optimal choice of a society that is concerned about agenda manipulation.

]]>We study the repeated implementation of social choice functions in environments with complete information and changing preferences. We define *dynamic monotonicity*, a natural but nontrivial dynamic extension of Maskin monotonicity, and show that it is necessary and almost sufficient for repeated Nash implementation, regardless of whether the horizon is finite or infinite and whether the discount factor is “large” or “small.”

The allocation and exchange of discrete resources, such as transplant organs, public housing, dormitory rooms, and many other resources for which agents have single-unit demand, is often conducted via direct mechanisms without monetary transfers. Incentive compatibility and efficiency are primary concerns when designing such mechanisms. We construct the full class of group strategy-proof and Pareto-efficient mechanisms and show that each of them can be implemented by endowing agents with control rights over resources. This new class, which we call trading cycles, contains new mechanisms as well as known mechanisms such as top trading cycles, serial dictatorships, and hierarchical exchange. We illustrate how one can use our construction to show what can and what cannot be achieved in a variety of allocation and exchange problems, and we provide an example in which the new trading-cycles mechanisms are more Lorenz equitable than all previously known mechanisms.

]]>Modern economies rely heavily on their infrastructure networks. These networks face threats ranging from natural disasters to human attacks. As networks are pervasive, the investments needed to protect them are very large; this motivates the study of targeted defense. What are the “key” nodes to defend to maximize functionality of the network? What are the incentives of individual nodes to protect themselves in a networked environment and how do these incentives correspond to collective welfare?

We first provide a characterization of optimal attack and defense in terms of two classical concepts in graph theory: *separators* and *transversals*. This characterization permits a systematic study of the *intensity of conflict* (the resources spent on attack and defense) and helps us identify a new class of networks—*windmill graphs*—that minimize conflict.

We then study security choices by individual nodes. Our analysis identifies the externalities and shows that the welfare costs of decentralized defense in networks can be very large.

Two of the most well known regularities observed in preferences under risk and uncertainty are ambiguity aversion and the Allais paradox. We study the behavior of an agent who can display *both* tendencies simultaneously. We introduce a novel notion of preference for hedging that applies to both objective lotteries and uncertain acts. We show that this axiom, together with other standard ones, is equivalent to a representation in which the agent (i) evaluates ambiguity using multiple priors, as in the model of Gilboa and Schmeidler, 1989, and (ii) evaluates objective lotteries by distorting probabilities, as in the rank dependent utility model, but using the worst from a set of distortions. We show that a preference for hedging is not sufficient to guarantee Ellsberg-like behavior if the agent violates expected utility for objective lotteries; we provide a novel axiom that characterizes this case, linking the distortions for objective and subjective bets.

This paper examines the interplay between career concerns and market structure. Ability and effort are complements: effort increases the probability that a skilled agent achieves a one-time breakthrough. Wages are based on assessed ability and on expected output. Effort levels at different times are strategic substitutes and, as a result, the unique equilibrium effort and wage paths are single-peaked with seniority. Moreover, for any wage profile, the agent works too little, too late. Commitment to wages by competing firms mitigates these inefficiencies. In that case, the optimal contract features piecewise constant wages and severance pay.

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