Eliciting Preferences to Assign Positions and Compensation

We describe strategy-proof rules for economies where an agent is assigned a position (e.g., a job) plus some of a divisible good. For the 2-agent–2-position case we derive a robust characterization. For the multi-agent–position case, many “arbitrary” such rules exist, so we consider additional requirements. By also requiring coalitional strategy-proofness or nonbossiness, the range of a solution is restricted to the point that such rules are not more complex than those for the Shapley–Scarf housing model (no divisible good). Third, we show that essentially only constant solutions are immune to manipulations involving “bribes.” Finally, we demonstrate a conflict between efficiency and strategy-proofness. The results extend to models (without externalities) in which agents share positions. Journal of Economic Literature Classification Numbers: C72, D70.     

Population-monotonicity and separability for economies with single-dipped preferences and the assignment of an indivisible object

We study two allocation models. In the first model, we consider the problem of allocating an infinitely divisible commodity among agents with single-dipped preferences. In the second model, a degenerate case of the first one, we study the allocation of an indivisible object to a group of agents. We consider rules that satisfy Pareto efficiency, strategy-proofness, and in addition either the consistency property separability or the solidarity property population-monotonicity. We show that the class of rules that satisfy Pareto efficiency, strategy-proofness, and separability equals the class of rules that satisfy Pareto efficiency, strategy-proofness, and non-bossiness. We also provide characterizations of all rules satisfying Pareto efficiency, strategy-proofness, and either separability or population-monotonicity. Since any such rule consists for the largest part of serial-dictatorship components, we can interpret the characterizations as impossibility results. Received: September 29, 1999; revised version: March 22, 2000     

Coalitional Strategy-Proof House Allocation

We consider house allocation without endowments. We show that there is a unique maximal domain including all strict preferences on which efficiency and coalitional strategy-proofness are compatible. A preference relation belongs to the unique maximal domain if it is a strict descending ranking of houses to a certain house and indifference holds over it and the remaining houses. We also show that on this domain mixed dictator-pairwise-exchange rules are the only rules satisfying efficiency and coalitional strategy-proofness. Journal of Economic Literature Classification Numbers: C78, D63, D71.     

The Pareto-dominant strategy-proof and fair rule for problems with indivisible goods

We study the problem of allocating a set of indivisible goods among a set of agents when monetary transfers are not allowed. We consider two interesting cases of this problem: (1) the supply of each object is exactly one; and (2) the supply of an object may be greater than one. Our central requirements are strategy-proofness and ex post fairness. We propose a particular rule satisfying strategy-proofness and no-envy (as well as equal treatment of equals). For the first case, it Pareto dominates any other rule satisfying strategy-proofness and equal treatment of equals. For the second case, it Pareto dominates any other rule satisfying strategy-proofness and no-envy.     

Consistent representative democracy

We study axioms which define “representative democracy” in an environment in which agents vote over a finite set of alternatives. We focus on a property that states that whether votes are aggregated directly or indirectly makes no difference. We call this property representative consistency. Representative consistency formalizes the idea that a voting rule should be immune to gerrymandering. We characterize the class of rules satisfying unanimity, anonymity, and representative consistency. We call these rules “partial priority rules.” A partial priority rule can be interpreted as a rule in which each agent can “veto” certain alternatives. We investigate the implications of imposing other axioms to the list specified above. We also study the partial priority rules in the context of specific economic models.     

Second price auctions on general preference domains: two characterizations

Auction theory usually assumes the quasi-linearity of individual preferences. We drop this assumption and define an extension of second price mechanisms that applies to general preferences. It turns out that the extended second price mechanisms are the only rules satisfying efficiency, strategy-proofness, and a mild non-imposition property. Their definition is simple just as much as the definition of usual second price mechanisms: everyone reports his maximum willingness to pay and the bidder whose reported value is highest buys the auctioned object for the price equal to the second highest reported value. The characterization is valid if efficiency is replaced by envy-freeness. I gratefully acknowledge an associate editor and two anonymous referees for their very helpful comments. Hiroki Saitoh and Shigehiro Serizawa independently obtain a result that is closely related to my main result (see, Remark in Sect. 1). I thank them for sending me the paper and communication, and Yuji Fujinaka for informing me about their work. I also thank the financial support by KAKENHI (19310031).     

Priorities in the location of multiple public facilities

A collective decision problem is described by a set of agents, a profile of single-peaked preferences over the real line and a number of public facilities to be located. We consider public facilities that do not suffer from congestion and are non-excludable. We characterize the class of rules satisfying Pareto-efficiency, object-population monotonicity and sovereignty. Each rule in the class is a priority rule that selects locations according to a predetermined priority ordering among “interest groups”. We characterize the subclasses of priority rules that respectively satisfy anonymity, avoid the no-show paradox, strategy-proofness and population-monotonicity. In particular, we prove that a priority rule is strategy-proof if and only if it partitions the set of agents into a fixed hierarchy. Any such rule can also be viewed as a collection of generalized peak-selection median rules, that are linked across populations, in a way that we describe.     

Profit sharing in unique Nash equilibrium: Characterization in the two-agent case

Two agents jointly operate a decreasing marginal returns technology to produce a private good. We characterize the class of output-sharing rules for which the labor-supply game has a unique Nash equilibrium. It consists of two families: rules of the serial type which protect a small user from the negative externality imposed by a large user, and rules of the reverse serial type, where one agent effectively employs the other agent's labor. Exactly two rules satisfy symmetry; a result in sharp contrast with Moulin and Shenker's characterization of their serial mechanism as the unique cost-sharing rule satisfying the same incentives property [Moulin, H., Shenker, S., 1992. Serial cost sharing. Econometrica 60 (5), 1009–1037]. We also show that the familiar stand-alone test characterizes the class of fixed-path methods under our incentives criterion [Friedman, E.J., 2004. Strong monotonicity in surplus sharing. Econ. Theory 23, 643–658].     

Efficient priority rules

We study the assignment of indivisible objects with quotas (universities, jobs, or offices) to a set of agents (students, job applicants, or professors). Each agent receives at most one object and monetary compensations are not possible. We characterize efficient priority rules by efficiency, strategy-proofness, and reallocation-consistency. Such a rule respects an acyclic priority structure and the allocations are determined using the deferred acceptance algorithm.     

Optimal pricing and capacity choice for a public service under risk of interruption

We develop rules for pricing and capacity choice for an interruptible service that recognize the interdependence between consumers’ perceptions of system reliability and their market behavior. Consumers post ex ante demands, based on their expectations on aggregate demand. Posted demands are met if ex post supply capacity is sufficient. However, if supply is inadequate all ex ante demands are proportionally interrupted. Consumers’ expectations of aggregate demand are assumed to be rational. Under reasonable values for the consumer’s degrees of relative risk aversion and prudence, demand is decreasing in supply reliability. We derive operational expressions for the optimal pricing rule and the capacity expansion rule. We show that the optimal price under uncertainty consists of the optimal price under certainty plus a markup that positively depends on the degrees of relative risk aversion, relative prudence and system reliability. We also show that any reliability enhancing investment—though lowering the operating surplus of the public utility—is socially desirable as long as it covers the cost of investment.     

The probabilistic serial mechanism with private endowments

A random assignment is ordinally efficient if it is not stochastically dominated with respect to individual preferences over sure objects. When there are no private endowments, the set of ordinally efficient random assignments is characterized by the eating algorithm (Bogomolnaia and Moulin, 2001). When there are private endowments, the main requirement is individual rationality; however, the eating algorithm fails to deliver this property. Our contribution is the natural generalization of the eating algorithm for this general class of problems. The family of this generalized eating algorithm characterizes the set of individually rational and ordinally efficient random assignments. A special solution in this family, the individually rational probabilistic serial (${\mathrm{PS}}^{\mathbf{IR}}$), also achieves a new fairness axiom, no justified-envy. However, it is not immune to strategic manipulation. We show that individual rationality, no justified-envy and strategy-proofness are incompatible.     

Games of Manipulation in Marriage Problems

We analyze the “equilibrium” outcomes of thepreference revelation gamesinduced byPareto efficientandindividually rationalsolutions in the context ofmarriage problems. We employ a Nash equilibrium refinement which allows deviations by a set of permissible coalitions, and show that the set of equilibrium outcomes coincides with a variant of the core that allows blocking by only permissible coalitions,Journal of Economic LiteratureClassification Numbers: C71, C78, D71, D78.     

WOULD AUSTRALIA–NEW ZEALAND BE A VIABLE CURRENCY UNION? EVIDENCE FROM INTERSTATE RISK‐SHARING PERFORMANCES

In this article, we first measure the potential welfare gains from perfect risk sharing among Australian states and New Zealand regions under possible unification. We show that New Zealand regions reap moderate gains from perfect risk sharing when they form a union with Australia, whereas for Australian states, the gains are somewhat similar to what they have attained at the intranational level. Second, we measure the extent of interstate risk sharing and intertemporal smoothing between the two countries. We are able to observe a substantial degree of intertemporal smoothing among Australian states and New Zealand regions, either alone or jointly, thus confirming the permanent income hypothesis. Further, unique to the risk‐sharing literature, we decompose the aggregate (nondiversifiable) output shocks into positive and negative components, in order to assess the strength of risk‐sharing mechanisms across business cycles. The study finds a virtual absence of risk sharing when Australia and New Zealand face negative aggregate fluctuations, raising doubts about the feasibility of the union, particularly during economic downturns. (JEL F41, F36)     

Consistent House Allocation

In practice we often face the problem of assigning indivisible objects (e.g., schools, housing, jobs, offices) to agents (e.g., students, homeless, workers, professors) when monetary compensations are not possible. We show that a rule that satisfies consistency, strategy-proofness, and efficiency must be an efficient generalized priority rule; i.e., it must adapt to an acyclic priority structure, except – maybe – for up to three agents in each object’s priority ordering. We are grateful to the Editor and an anonymous referee for helpful comments and suggestions. L. Ehlers acknowledges financial support from the SSHRC (Canada)     

Resource-monotonic allocation when preferences are single-peaked

Summary. We consider the problem of allocating an infinitely divisible commodity among a group of agents with single-peaked preferences. Thomson (1994a), S?nmez (1994), and Moulin (1999) introduce three different resource-monotonicity conditions. In each characterization they derive, the axioms are independent. Under Pareto-optimality, the three resource-monotonicity conditions are equivalent. We investigate whether the interchange of these conditions still yields a valid characterization, and when the characterization still holds, whether it is a tight result or not. We strengthen each of the results, that is either the used resource-monotonicity condition can be replaced by a weaker one, or by using another resource-monotonicity condition, the result is not tight. Our main result is that when at least three agents are present, the class of fixed-path rationing methods is characterized by weak one-sided resource-monotonicity, strategy-proofness, and consistency. Received: April 24, 2000; revised version: April 10, 2001     

Coalitional Strategy-Proofness in Economies with Single-Dipped Preferences and the Assignment of an Indivisible Object

We study two allocation models. In the first model, we consider the problem of allocating an infinitely divisible commodity among agents with single-dipped preferences. In the second model, a degenerate case of the first one, we study the allocation of an indivisible object to a group of agents. Our main result is the characterization of the class of Pareto optimal and coalitionally strategy-proof allocation rules. Alternatively, this class of rules, which largely consists of serially dictatorial components, can be characterized by Pareto optimality, strategy-proofness, and weak non-bossiness (in terms of welfare). Furthermore, we study properties of fairness such as anonymity and no-envy. Journal of Economic Literature Classification Numbers: D63, D71.     

A solution to the random assignment problem on the full preference domain

We consider the problem of allocating a set of indivisible objects to agents in a fair and efficient manner. In a recent paper, Bogomolnaia and Moulin consider the case in which all agents have strict preferences, and propose the probabilistic serial (PS) mechanism; they define a new notion of efficiency, called ordinal efficiency, and prove that the probabilistic serial mechanism finds an envy-free ordinally efficient assignment. However, the restrictive assumption of strict preferences is critical to their algorithm. Our main contribution is an analogous algorithm for the full preference domain in which agents are allowed to be indifferent between objects. Our algorithm is based on a reinterpretation of the PS mechanism as an iterative algorithm to compute a “flow” in an associated network. In addition we show that on the full preference domain it is impossible for even a weak strategyproof mechanism to find a random assignment that is both ordinally efficient and envy-free.     

k-Price Auctions

In this paper we analyze the equilibria structure of k-price auctions, k ≥ 3, under the independent-private-value assumption. We discuss agents with an arbitrary attitude toward risk. That is, agents may be risk averse or risk seeking, or they may have an alternating attitude toward risk. We provide a characterization of a continuous symmetric equilibrium, prove that there exists at most one such equilibrium, and show that every such equilibrium is differentiable and increasing. We also show some additional general properties of the equilibrium strategies in these auctions. Journal of Economic Literature Classification Numbers: C72, C73, D83.     

Half empty, half full and why we can agree to disagree forever

Aumann [Aumann R., 1976. Agreeing to disagree. Annals of Statisitics 4, 1236–1239] derives his famous we cannot agree to disagree result under the assumption that people are expected utility (=EU) decision makers. Motivated by empirical evidence against EU theory, we study the possibility of agreeing to disagree within the framework of Choquet expected utility (=CEU) theory which generalizes EU theory by allowing for ambiguous beliefs. As our first main contribution, we show that people may well agree to disagree if their Bayesian updating of ambiguous beliefs is psychologically biased in our sense. Remarkably, this finding holds regardless of whether people with identical priors apply the same psychologically biased Bayesian update rule or not. As our second main contribution, we develop a formal model of Bayesian learning under ambiguity. As a key feature of our approach the posterior subjective beliefs do, in general, not converge to “true” probabilities which is in line with psychological evidence against converging learning behavior. This finding thus formally establishes that CEU decision makers may even agree to disagree in the long-run despite the fact that they always received the same information.     

Contracts and externalities: How things fall apart

A single principal interacts with several agents, offering them contracts. The crucial assumption of this paper is that the outside-option payoffs of the agents depend positively on how many uncontracted or “free” agents there are. We study how such a principal, unwelcome though he may be, approaches the problem of contract provision to agents when coordination failure among the latter group is explicitly ruled out. Two variants are considered. When the principal cannot re-approach agents, there is a unique equilibrium, in which contract provision is split up into two phases. In phase 1, simultaneous offers at good (though varying) terms are made to a number of agents. In phase 2, offers must be made sequentially, and their values are “discontinuously” lower: they are close to the very lowest of all the outside options. When the principal can repeatedly approach the same agent, there is a multiplicity of equilibria. In some of these, the agents have the power to force delay. They can hold off the principal's overtures temporarily, but they must succumb in finite time. In both models, despite being able to coordinate their actions, agents cannot resist an “invasion” by the principal and hold to their best payoff. It is in this sense that “things [eventually] fall apart”.