A Solution for General Exchange Markets with Indivisible Goods when Indifferences are Allowed

It is well known that the core of an exchange market with indivisible goods is always non empty, although it may contain Pareto inefficient allocations. The strict core solves this shortcoming when indifferences are not allowed, but when agents' preferences are weak orders the strict core may be empty. On the other hand, when indifferences are allowed, the core or the strict core may fail to be stable sets, in the von Neumann and Morgenstern sense. We introduce a new solution concept that improves the behaviour of the strict core, in the sense that it solves the emptiness problem of the strict core when indifferences are allowed in the individuals' preferences and whenever the strict core is non-empty, our solution is included in it. We define our proposal, the MS-set, by using a stability property (m-stability) that the strict core fulfills. Finally, we provide a min-max interpretation for this new solution

Sharing the cost of maximum quality optimal spanning trees

Minimum cost spanning tree problems have been widely studied in operation research and economic literature. Multi-objective optimal spanning trees provide a more realistic representation of different actual problems. Once an optimal tree is obtained, how to allocate its cost among the agents defines a situation quite different from what we have in the minimum cost spanning tree problems. In this paper, we analyze a multi-objective problem where the goal is to connect a group of agents to a source with the highest possible quality at the cheapest cost. We compute optimal networks and propose cost allocations for the total cost of the project. We analyze properties of the proposed solution; in particular, we focus on coalitional stability (core selection), a central concern in the literature on minimum cost spanning tree problems.This work is supported by the Spanish Ministerio de Economía y Competitividad, under project ECO2016-77200-P. Financial support from the Generalitat Valenciana (BEST/2019 Grants) to visit the UNSW is also acknowledged

Equalizing solutions for bankruptcy problems revisited

When solving bankruptcy problems through equalizing solutions, agents with small claims prefer to distribute the estate according to the Constrained Equal Awards solution, while the adoption of the Constrained Equal Losses solution is preferred by agents with high claims. Therefore, the determination of which is the central claimant, as a reference to distinguish the agents with a high claim from those with a low claim, is a relevant question when designing hybrid solutions, or new methods to distribute the available estate in a bankruptcy problem. We explore the relationship between the equal awards parameter λ and the equal losses parameter μ that characterize the two solutions. We show that the central claimant is fully determined by these parameters. In addition, we explore how to compute these parameters and present optimization problems that provide the Constrained Equal Awards and the Constrained Equal Losses solutions.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature

Participation and Solidarity in Redistribution Mechanisms

Following Bossert (1995), we consider a model where personal income depends on two different characteristics: skills and effort. Luttens (2010) introduces claims that individuals have over aggregate income and that only depend on the effort they exert. Moreover, he proposes redistribution mechanisms in which solidarity is based on changes in a lower bound on what every individual deserves according to these claims: the so-called minimal rights (O’Neill 1982). A debatable consequence in one of Luttens’ mechanisms is that “the poorest individuals might up with a negative income” (Luttens 2010); that is, this mechanism does not satisfy participation, which turns out to be incompatible with claims feasibility, under Luttens’ assumptions. We present a new solidarity axiom that is compatible both with participation and claims feasibility, and we provide a mechanism satisfying these properties and our new additive solidarity axiom. Moreover, our mechanism satisfies additional properties, as priority, or respect of minimal rights.This has been partially supported by the Spanish Ministry of Economy and Competitiveness funds under Project ECO2013-43119 and by Universitat Rovira i Virgili, Banco Santander and Generalitat de Catalunya under the project 2011LINE-06

A proportional approach to claims problems with a guaranteed minimum

In distribution problems, and specifically in bankruptcy issues, the Proportional (P) and the Egalitarian (EA) divisions are two of the most popular ways to resolve the conflict. Nonetheless, when using the egalitarian division, agents may receive more than her claim. We propose a compromise between the proportional and the egalitarian approaches by considering the restriction that no one receives more than her claim. We show that the most egalitarian compromise fulfilling this restriction ensures a minimum amount to each agent. We also show that this compromise can be interpreted as a process that works in two steps as follows: first, all agents receive an equal share up to the smallest claim if possible (egalitarian distribution), and then, the remaining estate (if any) is allocated proportionally to the remaining claims (proportional distribution). Finally, we obtain that the recursive application of this process finishes at the Constrained Equal Awards solution (CEA).Financial support from Universitat Rovira i Virgili, Banco Santander and Generalitat de Catalunya under Project 2011LINE-06 and the Barcelona GSE

Mediation in claims problems

Mediation is a dispute resolution process whereby agents reach a mutually acceptable agreement among different proposals that satisfy a set of principles. This paper provides a natural way of coming to such agreements in claims problems. In our approach, mediation combines (i) a set of fair properties (legitimate principles); and (ii) a criterion for delimiting the admissible manners of distributing the endowment, that is determined by the mediator expressing the two (dual) points of view to face such problems: awards and losses. These dual views define a lower and an upper bounds on awards, which are used to implement the so-called Double Recursive Process. We find that this process concludes at the midpoint between the two dual points of view. Finally, we argue that the criterion of the mediator could be established throughout Lorenz domination. In so doing, we retrieve the average of old and well-known rules.Financial support from Universitat Rovira i Virgili, Banco Santander and Generalitat de Catalunya under project 2011LINE-06

A non-cooperative approach to the folk rule in minimum cost spanning tree problems

This paper deals with the problem of finding a way to distribute the cost of a minimum cost spanning tree problem between the players. A rule that assigns a payoff to each player provides this distribution. An optimistic point of view is considered to devise a cooperative game. Following this optimistic approach, a sequential game provides this construction to define the action sets of the players. The main result states the existence of a unique cost allocation in subgame perfect equilibria. This cost allocation matches the one suggested by the folk rule.The authors thank the support of the Spanish Ministry of Science, Innovation and Universities, the Spanish Ministry of Economy and Competitiveness, the Spanish Agency of Research, co-funded with FEDER funds, under the projects ECO2016-77200-P, ECO2017-82241-R, ECO2017-87245-R, PID2021-128228NB-I00, Consellería d’Innovación, Universitats, Ciencia i Societat Digital, Generalitat Valenciana [grant number AICO/2021/257], and Xunta de Galicia (ED431B 2019/34)

Cost sharing solutions defined by non-negative eigenvectors

The problem of sharing a cost M among n individuals, identified by some characteristic ci∈R+,ci∈R+, appears in many real situations. Two important proposals on how to share the cost are the egalitarian and the proportional solutions. In different situations a combination of both distributions provides an interesting approach to the cost sharing problem. In this paper we obtain a family of (compromise) solutions associated to the Perron’s eigenvectors of Levinger’s transformations of a characteristics matrix A. This family includes both the egalitarian and proportional solutions, as well as a set of suitable intermediate proposals, which we analyze in some specific contexts, as claims problems and inventory cost games.Financial support from Spanish Ministry of Economy and Competitiveness under Project ECO2013-43119 is gratefully acknowledged. Silva-Reus also acknowledges financial support from the Generalitat Valenciana, Spain under Project PROMETEO/2009/068

From Bargaining Solutions to Claims Rules: A Proportional Approach

Agents involved in a conflicting claims problem may be concerned with the proportion of their claims that is satisfied, or with the total amount they get. In order to relate both perspectives, we associate to each conflicting claims problem a bargaining-in-proportions set. Then, we obtain a correspondence between classical bargaining solutions and usual claims rules. In particular, we show that the constrained equal losses, the truncated constrained equal losses and the contested garment (Babylonian Talmud) rules can be obtained throughout the Nash bargaining solution.Financial support from Universitat Rovira i Virgili, Banco Santander and Generalitat de Catalunya under project 2011LINE-06, Ministerio de Ciencia e Innovación under project ECO2011-24200 and from the Spanish Ministry of Economy and Competitiveness under project ECO2013-43119 are gratefully acknowledged

Folk solution for simple minimum cost spanning tree problems

A minimum cost spanning tree problem analyzes how to efficiently connect a group of individuals to a source. Once the efficient tree is obtained, the addressed question is how to allocate the total cost among the involved agents. One prominent solution in allocating this minimum cost is the so-called Folk solution. Unfortunately, in general, the Folk solution is not easy to compute. We identify a class of mcst problems in which the Folk solution is obtained in an easy way. This class includes elementary cost mcst problems.Financial support from Generalitat de Catalunya (2014SGR325 and 2014SGR631) and Ministerio de Economía y Competitividad (ECO2013-43119-P) is acknowledged