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].     

Lorenz rankings of rules for the adjudication of conflicting claims

For the adjudication of conflicting claims, we develop three general approaches to obtain Lorenz rankings of rules. Our first approach concerns a parameterized family that contains several important rules (Thomson in Soc Choice Welf 31:667?C692, 2008). We give a condition that the parameters defining two members of the family should satisfy for one of them to Lorenz dominate the other. Our second approach exploits the concept of ??consistency?? (Young in Math Oper Res 12:398?C414, 1987). We derive a criterion to deduce Lorenz domination for arbitrarily many claimants from Lorenz domination in the two-claimant case. Our third approach is based on the notion of an ??operator?? on the space of rules (Thomson and Yeh in J Econ Theory 143:177?C198, 2008). We develop conditions under which operators preserve the Lorenz order, or reverse it. As corollaries of our general theorems, we obtain rankings of most of the rules that have been discussed in the literature.     

Probabilistic assignment of objects: Characterizing the serial rule

We study the problem of assigning a set of objects to a set of agents, when each agent receives one object and has strict preferences over the objects. In the absence of monetary transfers, we focus on the probabilistic rules, which take the ordinal preferences as input. We characterize the serial rule, proposed by Bogomolnaia and Moulin (2001) [2]: it is the only rule satisfying sd efficiency, sd no-envy, and bounded invariance. A special representation of feasible assignment matrices by means of consumption processes is the key to the simple and intuitive proof of our main result.     

Reflecting inequality of claims in gains and losses

We consider the problem of dividing a resource among a group of agents who have conflicting claims on it. We follow the axiomatic approach and investigate the class of rules satisfying claims-inequality and claims-order preservation in gains and losses. We show that these axioms single out the proportional rule when there are more than three agents. This result confirms the central role of this rule and furthers our understanding of it in claims problems.     

Strategy-proof Location on a Network

We consider rules that choose a location on a graph (e.g. a road network) based on agents' single-peaked preferences. First, we characterize the class of strategy-proof, onto rules when the graph is a tree. Such a rule is based on a collection of generalized median voter rules (Moulin, 1980) satisfying a consistency condition. Second, we characterize such rules for graphs containing cycles. We show that while such a rule is not necessarily dictatorial, the existence of a cycle grants some agent an amount of decisive power, unlike the case of trees. Rules for this case can be described in terms of a subclass of such rules for trees. Journal of Economic Literature Classification Numbers: C72, D78.     

Consistent strategy-proof assignment by hierarchical exchange

We characterize the family of efficient, consistent, and strategy-proof rules in house allocation problems. These rules follow an endowment inheritance and trade procedure as in Pápai’s hierarchical exchange rules (Pápai in Econometrica 68, 1403–1433, 2000) and closely resemble Ergin’s priority rules (Ergin in Econometrica 70, 2489–2497, 2002). We prove that if there are at least four objects, these are the only rules that are efficient in two-agent problems, $2$ -consistent, and strategy-proof. A corollary is that these three basic properties together imply the full requirements of efficiency, consistency, group strategy-proofness, and reallocation-proofness.     

A new solution to the problem of adjudicating conflicting claims

Summary. For the problem of adjudicating conflicting claims, we consider the requirement that each agent should receive at least 1/n his claim truncated at the amount to divide, where n is the number of claimants (Moreno-Ternero and Villar, 2004a). We identify two families of rules satisfying this bound. We then formulate the requirement that for each problem, the awards vector should be obtainable in two equivalent ways, (i) directly or (ii) in two steps, first assigning to each claimant his lower bound and then applying the rule to the appropriately revised problem. We show that there is only one rule satisfying this requirement. We name it the “ rule”, as it is obtained by a recursion. We then undertake a systematic investigation of the properties of the rule.Received: 7 September 2004, Revised: 21 April 2005, JEL Classification Numbers: C79, D63, D74.William Thomson: Correspondence toWe thank Christopher Chambers, Youngsub Chun, Tarík Kara, Çağatay Kayí, Juan Moreno-Ternero, Toyotaka Sakai, and Michel Truchon for their comments. We also thank a referee for useful comments. This paper was presented at Columbia University, CORE, Bilkent University, Sabancí University, Université Laval, and Caltech, and at the Mallorca Review of Economic Design meeting. Thomson acknowledges support from the NSF under grant SES-0214691.     

Asymmetric parametric division rules

We describe and characterize the family of asymmetric parametric division rules for the adjudication of conflicting claims on a divisible homogeneous good. As part of the characterization, we present two novel axioms which restrict how a division rule indirectly allocates between different versions of the same claimant. We also show that such division rules can alternately be represented as the maximization of an additively separable social welfare function.     

Public Goods Provision: On Generalizing the Jackson–Moulin Mechanism

Jackson and Moulin (1992) proposed a simple mechanism to implement a wide class of cost‐sharing rules for the provision of a binary public good. Bag (1997) generalized this mechanism to divisible public goods under the assumption of “constant marginal benefit.” This paper generalizes the Jackson–Moulin mechanism to a broader setting, including the cases of both decreasing and constant marginal benefit. Moreover, this paper shows the impossibility of generalizing the mechanism further.     

Convergence under replication of rules to adjudicate conflicting claims

We study the behavior of rules for the adjudication of conflicting claims when there is a large number of claimants with small claims. We model such situations by replicating some basic problem. We show that under replication, the random arrival rule [Math. Soc. Sci. 2 (1982) 345] behaves like the proportional rule, the rule that is the most often recommended in this context. Also, under replication, the minimal overlap rule [Math. Soc. Sci. 2 (1982) 345] behaves like the constrained equal losses rule, the rule that selects a division at which all claimants experience equal losses subject to no-one receiving a negative amount.     

Beyond Moulin mechanisms

The only known general technique for designing truthful and approximately budget-balanced cost-sharing mechanisms with good efficiency or computational complexity properties is due to Moulin [1999. Incremental cost sharing: Characterization by coalition strategy-proofness. Soc. Choice Welfare 16 (2), 279–320]. For many fundamental cost-sharing applications, however, Moulin mechanisms provably suffer from poor budget-balance, poor economic efficiency, or both.We propose acyclic mechanisms, a new framework for designing truthful and approximately budget-balanced cost-sharing mechanisms. Acyclic mechanisms strictly generalize Moulin mechanisms and offer three important advantages. First, it is easier to design acyclic mechanisms than Moulin mechanisms: many classical primal-dual algorithms naturally induce a non-Moulin acyclic mechanism with good performance guarantees. Second, for important classes of cost-sharing problems, acyclic mechanisms have exponentially better budget-balance and economic efficiency than Moulin mechanisms. Finally, while Moulin mechanisms have found application primarily in binary demand games, we extend acyclic mechanisms to general demand games, a multi-parameter setting in which each bidder can be allocated one of several levels of service.     

Strategy-proof risk sharing

We consider risk sharing problems with a single good and a finite number of states. Agents have a common prior and their preferences are represented in the expected utility form and are risk averse. We study efficient and individually rational risk sharing rules satisfying strategy-proofness, the requirement that no one can ever benefit by misrepresenting his preference. When aggregate certainty holds, we show that “fixed price selections” from Walrasian correspondence are the only rules satisfying efficiency, individual rationality, and strategy-proofness. However, when aggregate uncertainty holds, we show that there exists no rule satisfying the three requirements. Moreover, in the two agents case, we show that dictatorial rules are the only efficient and strategy-proof rules. Dropping the common prior assumption in the model, we show that this assumption is necessary and sufficient for the existence of rules satisfying the three main requirements in the two agents and aggregate certainty case.     

Asymmetric rules for claims problems without homogeneity

We introduce a general class of rules for claims problems, called the difference rules, and demonstrate that a rule satisfies composition down and composition up if and only if it is a difference rule. We show that these rules are very simple to describe when there are two agents. In a variable population framework, we introduce a family of rules satisfying consistency, composition down, and composition up, which we term the logarithmic-proportional rules. These rules satisfy neither symmetry nor homogeneity.     

Reduced game and converse consistency

The initiating points of the current paper are the axiomatic characterizations, in terms of consistency, of the equal allocation of nonseparable cost value (by Moulin), the Shapley value (by Hart and Mas-Colell), and the prenucleolus (by Orshan). The basic axioms are the same, but three different reduced games can be used to distinguish these three solutions. The main purpose of the paper is to illustrate that besides the definitions of reduced games are different, the axiom converse consistency also plays an important role to distinguish these three solutions.     

Group identification with (incomplete) preferences

We consider the problem of identifying members of a group based on individual opinions. Since agents do not have preferences in the model, properties of rules that concern preferences (e.g., strategy‐proofness and efficiency) have not been studied in the literature. We fill this gap by working with a class of incomplete preferences derived directly from opinions. Our main result characterizes a new family of group identification rules, called voting‐by‐equitable‐committees rules, using two well‐known properties: strategy‐proofness and equal treatment of equals. Our family contains as a special case the consent rules (Samet & Schmeidler. J. Econ. Theory, 110 (2003), pp. 213–233), which are symmetric and embody various degrees of liberalism and democracy; and it also includes dictatorial and oligarchic rules that value agents’ opinions differently. In the presence of strategy‐proofness, efficiency turns out to be equivalent to non‐degeneracy (i.e., any agent may potentially be included or excluded from the group). This implies that a rule satisfies strategy‐proofness, efficiency, and equal treatment of equals if, and only if, it is a non‐degenerate voting‐by‐equitable‐committees rule.     

Composition, Securement, and Concede-and-divide

Concede-and-divide is a widely accepted procedure to solve the problem of adjudicating two conflicting claims. In this paper we show that this procedure can be characterized by combining three standard properties in the literature: self-duality, lower securement, and restricted composition up. We also show that self-duality can be replaced by the dual properties of lower securement and restricted composition up and that both characterization results are tight.     

Strategy Proof Uniform Effort Sharing Schemes For Transfrontier Pollution Problems

Uniform effort sharing rules for transfrontier pollution problems, like the popular equal percentage reduction arrangement, do not result in a cost efficient allocation of emission abatement efforts. In addition, they may violate voluntary participation constraints if the uniform effort level is decided upon by means of ordinary majority vote. In contrast to ordinary majority vote, I consider in this paper the so-called conservative mechanism by Moulin (1994) which picks the smallest revealed effort level in stead of the median. The conservative mechanism always respects a weak participation constraint. Moreover, it is coalitionally strategy proof meaning that no individual player, or group of players, can achieve a better outcome by misrepresenting its preferences for environmental quality. In order to remedy the cost inefficiency of the equal percentage arrangements, I propose to apply the conservative mechanism to the choice of a uniform emission tax rate. Simulations for the greenhouse effect indicate that the latter mechanism does considerably better than the traditional equal percentage arrangement.     

Existence of equilibrium in common agency games with adverse selection

We establish the existence of subgame perfect equilibria in general menu games, known to be sufficient to analyze common agency problems. Our main result states that every menu game satisfying enough continuity properties has a subgame perfect equilibrium. Despite the continuity assumptions that we make, discontinuities naturally arise due to the absence, in general, of continuous optimal choices for the agent. Our approach, then, is based on (and generalizes) the existence theorem of [Simon, L., Zame, W., 1990. Discontinuous games and endogenous sharing rules. Econometrica 58 (4), 861–872] designed for discontinuous games.     

Intertemporally Consistent Population Ethics: Birth-date Dependent Classical Principles

This paper shows that, in a partially welfarist framework that permits discounting, perperiod social evaluations can be consistent with a timeless social ordering only if social principles lead to the repugnant conclusion . The same result applies if per-period social evaluations are replaced by forward-looking evaluations (social orderings that, in a given period, depend on present and future utilities only). This is the case because geometric classical generalized utilitarian principles are the only social principles satisfying these intertemporal consistency conditions together with some basic assumptions. The conclusion to be drawn from this paper is that history must matter to some extent if social-evaluation principles are to be ethically acceptable.
JEL Classification Numbers: D63, D71     

Egalitarian division under Leontief Preferences

We consider the problem of fairly dividing $l$ divisible goods among $n$ agents with the generalized Leontief preferences. We propose and characterize the class of generalized egalitarian rules which satisfy efficiency, group strategy-proofness, anonymity, resource monotonicity, population monotonicity, envy-freeness and consistency. On the Leontief domain, our rules generalize the egalitarian-equivalent rules with reference bundles. We also extend our rules to agent-specific and endowment-specific egalitarian rules. The former is a larger class of rules satisfying all the previous properties except anonymity and envy-freeness. The latter is a class of efficient, group strategy-proof, anonymous and individually rational rules when the resources are assumed to be privately owned.