Regular Population Monotonic Allocation Schemes and the Core

A subclass of games with population monotonic allocation schemes is studied, namely games with regular population monotonic allocation schemes (rpmas). We focus on the properties of these games and we prove the coincidence between the core and both the Davis-Maschler bargaining set and the Mas-Colell bargaining set.rpmas, bargaining set, pmas, tu-game

Regular population monotonic allocation schemes and the core

A subclass of games with population monotonic allocation schemes is studied, namely games with regular population monotonic allocation schemes (rpmas). We focus on the properties of these games and we prove the coincidence between the core and both the Davis-Maschler bargaining set and the Mas-Colell bargaining set- En aquest article s'estudia una subclase dels jocs cooperatius amb esquemes de distribució monótons des del punt de vista poblacional, i que anomenem jocs amb esquemes de distribució regulars. L'anàlisi es centra en les propietats d'aquests jocs i, com a resultat principal, es demostra que el nucli del joc coincideix amb el conjunt de negociació de Davis-Maschler, així com també amb el conjunt de negociació de Mas-Colell

Coalitionally Monotonic Set-solutions for Cooperative TU Games

A static comparative study on set-solutions for cooperative TU games is carried out. The analysis focuses on studying the compatibility between two classical and reasonable properties introduced by Young (1985) in the context of single valued solutions, namely core-selection and coalitional monotonicity. As the main result, it is showed that coalitional monotonicity is not only incompatible with the core-selection property but also with the bargaining-selection property. This new impossibility result reinforces the trade-off between these kinds of interesting and intuitive economic properties. Positive results about compatibility between desirable economic properties are given replacing the core- selection requirement by the core-extension property.core-extension, bargaining-selection, set-solution, coalitional monotonicity, core-selection

The proportional distribution in a cooperative model with external opportunities

[cat] En aquest article es considera un problema de cooperació entre agents on cada agent realitza una contribució (diners, capital, treball, esforç) per tal d'obtenir un benefici comú a repartir. El repartiment proporcional respecte a les contribucions és una distribució que pertany al nucli del joc cooperatiu associat. A partir d'aquest model bàsic s'introdueix un agent extern que pot realitzar una determinada aportació que serveix per avaluar el potencial benefici de cada subcoalició d'agents si aquest nou agent finalment entrés. Aquesta anàlisi pot produir que el poder relatiu dels agents hagi variat. en concret s'avalua si la distribució proporcional és encara robusta des del punt de vista de la seva pertinença al conjunt de negociació. Amb aquest objectiu, analitzem el problema utilitzant el model de joc cooperatius amb estructura de coalició. Donat que, en general, la distribució proporcional, no pertany al conjunt de negociació, s'estudia una condició suficient per a que així sigui. També enunciem una condició necessària, i finalment es proposa una condició suficient que garanteix que el repartiment proporcional és la única distribució existent dins del conjunt de negociació.[eng] We study a cooperative problem where agents contribute a certain amount of money or capital in order to obtain a surplus. The proportional distribution with respect to the contributions of players is a core element of the cooperative game associated. Within this basic model, an external agent is introduced in order to evaluate the potential profit of every subcoalition of agents in the case this new agent enters. This analysis can produce that the relative bargaining power of agents may be modified. In particular, we evaluate whether the proportional distribution is still a robust proposal from the point of view of the bargaining set of a cooperative game with coalition structure (Davis and Maschler, 1963). Since, in general, the proportional distribution fails to be a bargaining set element of this game, a sufficient condition for the proportional allocation to belong to the bargaining is stated. A necessary condition is also analysed. Finally, we state a sufficient condition that guarantees the proportional distribution to be the unique element of the bargaining set of the associated game with coalition structure

The incentive core in co-investment problems

We study resource-monotonicity properties of core allocations in coinvestment problems: those where a set of agents pool their endowments of a certain resource or input in order to obtain a joint surplus or output that must be allocated among the agents. We analyze whether agents have incentives to raise their initial contribution (resource-monotonicity). We focus not only on looking for potential incentives to agents who raise their contributions, but also in not harming the payoffs to the rest of agents (strong monotonicity property). A necessary and suficient condition to fulfill this property is stated and proved. We also provide a subclass of coinvestment problems for which any core allocation satisfies the aforementioned strong resource-monotonicity property. Moreover, we introduce the subset of core allocations satisfying this condition, namely the incentive core

Core allocations in Co-investment problems

In a co-investment problem a set of agents face a surplus-sharing situation with a single input and a single output exhibiting increasing average returns. All agents contribute their respective inputs and expect part of the collective output. Focusing on the core of the problem, we analyze whether a core allocation of the output is acceptable or compatible with a variation on input contributions, where larger payoffs are expected by those agents whose contribution is increased. We state a necessary and sufficient condition for a core allocation to be acceptable. We also introduce and study the acceptable core, that is, those core allocations acceptable with respect to any possible increase of inputs. Finally we axiomatically characterize when a set-solution that contains acceptable core allocations shrinks into the proportional allocation

The core and the steady bargaining set for convex games

Within the class of superadditive cooperative games with transferable utility, the convexity of a game is characterized by the coincidence of its core and the steady bargaining set. As a consequence it is also proved that convexity can also be characterized by the coincidence of the core of a game and the modi ed Zhou bargaining set (Shimomura, 1997

Sequential decisions in allocation problems

In the context of cooperative TU-games, and given an order of players, we consider the problem of distributing the worth of the grand coalition as a sequential decision problem. In each step of the process, upper and lower bounds for the payoff of the players are required related to successive reduced games. Sequentially compatible payoffs are defined as those allocation vectors that meet these recursive bounds. The core of the game is reinterpreted as a set of sequentially compatible payoffs when the Davis-Maschler reduced game is considered (Th.1). Independently of the reduction, the core turns out to be the intersection of the family of the sets of sequentially compatible payoffs corresponding to the different possible orderings (Th.2), so it is in some sense order-independent. Finally, we analyze advantageous properties for the first player.core, reduced game, sequential allocation, tu-game

Generalized rationing problems and solutions

An extension of the standard rationing model is introduced. Agents are not only identified by their respective claims on some amount of a scarce resource, but also by some exogenous ex-ante conditions (initial stock of resource or net worth of agents, for instance), different from claims. Within this framework, we define a generalization of the constrained equal awards rule. We provide two different characterizations of this generalized rule. Finally, we use the corresponding dual properties to characterize a generalization of the constrained equal losses rule

Rationing problems with payoff thresholds

An extension of the standard rationing model is introduced. Agents are not only identi fied by their respective claims over some amount of a scarce resource, but also by some payoff thresholds. These thresholds introduce exogenous differences among agents (full or partial priority, past allocations, past debts, ...) that may influence the final distribution. Within this framework we provide generalizations of the constrained equal awards rule and the constrained equal losses rule. We show that these generalized rules are dual from each other. We characterize the generalization of the equal awards rule by using the properties of consistency, path-independence and compensated exemption. Finally, we use the duality between rules to characterize the generalization of the equal losses solution