ON THE NEUTRALITY OF COALITION FORMATION IN A PURE BARGAINING PROBLEM*

We consider the sequential bargaining game à la Stahl–Binmore–Rubinstein with random proposers, juxtaposing an ex ante coalition formation stage to their bargaining game. On the basis of the expected outcomes in the negotiation over how to split a dollar, players can form coalitions in a sequential manner, within each of which they can redistribute their payoffs. It turns out that the grand coalition does form, and that each player receives his discounted expected payoff, which is obtained by playing as a single player in the negotiation, although there could be many equilibria in the bargaining stage.     

Buyer groups as strategic commitments

Buyer cooperatives, buyer alliances, and horizontal mergers are often perceived as attempts to increase buyer power. In contrast to prior research emphasizing group size, I show that even small buyer groups composed of buyers with heterogeneous preferences can increase price competition among rival sellers by committing to purchase exclusively from one seller. Without transfer payments, at least one buyer group exists for each pair of sellers and buyer groups membership is chosen to achieve indifference between the two sellers. With transfer payments, and just two sellers, the grand coalition is a coalition-proof subgame perfect equilibrium (CP-SPNE), though equilibria with arbitrarily many buyer groups also exist. With three sellers (and with more sellers when the distribution of buyers is symmetric), a CP-SPNE always exists, all coalition-proof equilibria are payoff equivalent and have at least one buyer group for each pair of firms, so the grand coalition is not an equilibrium.     

On the Least Core and the Mas-Colell Bargaining Set

We show that the least core of a TU coalitional game with a finite set of players is contained in the Mas-Colell bargaining set. This result is extended to games with a measurable space of players in which the worth of the grand coalition is at least that of any other coalition in the game. As a consequence, we obtain an existence theorem for the Mas-Colell bargaining set in TU games with a measurable space of players. Journal of Economic Literature Classification Number: C71.     

Cleaner Technologies and the Stability of International Environmental Agreements

This paper shows that if countries are farsighted when deciding whether to defect from a coalition, then the implementation of cleaner technologies, as embodied by a reduction in the emission per output ratio, may either improve or jeopardize the chances of reaching an international environmental agreement. A small change in the emission per output ratio can result in a discrete jump in the stable size of a coalition and global welfare evaluated under the stable coalition size. In the case of three countries, the grand coalition may be destabilized by the implementation of cleaner technologies, ultimately resulting in higher global emissions and lower global welfare. In the case of more than three countries, implementing cleaner technologies may result in a discrete jump, either upward or downward, of the largest stable coalition size and welfare. We examine both, the case of a flow and that of a stock pollutant. In the latter case, we show that the higher the stock of pollution at the instant when the cleaner technology is implemented, the more likely that a grand coalition of three countries is destabilized. Measures that enhance the natural rate of decay of stock pollutants are shown to have similar effects on the size of stable coalitions to reductions in the emission per output ratio.     

Efficiency in coalition games with externalities

A natural extension of superadditivity is not sufficient to imply that the grand coalition is efficient when externalities are present. We provide a condition, analogous to convexity, that is sufficient for the grand coalition to be efficient and show that this also implies that the (appropriately defined) core is nonempty. Moreover, we propose a mechanism which implements the most efficient partition for all coalition formation games and characterizes the resulting payoff division.     

Efficiency in coalition games with externalities

A natural extension of superadditivity is not sufficient to imply that the grand coalition is efficient when externalities are present. We provide a condition, analogous to convexity, that is sufficient for the grand coalition to be efficient and show that this also implies that the (appropriately defined) core is nonempty. Moreover, we propose a mechanism which implements the most efficient partition for all coalition formation games and characterizes the resulting payoff division.     

A game-theoretic model of coalition formation among primates

This paper models the coalition formation process among primates as a sequential game. The population consists of individuals having distinct social ranks which is determined by the individual’s resource holding potential. Each member of the population is interested in gaining access to a food resource, either individually or via a coalition. At any given stage of the game, a player can either propose a specific coalition or he can be proposed to in order to join one. Hence, the strategy of a player consists of a sequence of decisions regarding who to propose to for the formation of a coalition and which proposals to accept or reject. We derive the preferences of the players over the various coalition structures under the assumption that the probability of a coalition to obtain the resource is given by a logistic distribution as a function of relative strengths of the players. We show that, given the primates’ strategic behavior, a variety of different coalition structures can emerge in equilibrium.      

Multilateral Bargaining Problems

In many situations in economics and political science there are gains from forming coalitions but conflict over which coalition to form and how to distribute the gains. This paper presents an approach to suchmultilateral bargaining problems. Asolutionto a multilateral bargaining problem specifies an agreement for each coalition that is consistent with the bargaining process in every coalition. We establish the existence of such solutions, show that they are determined by reservation prices, and characterize these reservation prices as the payoffs ofsubgame perfect equilibrium outcomesof a non-cooperative bargaining model.Journal of Economic LiteratureClassification Numbers: C71, C72, C78.     

A Theory of Gradual Coalition Formation

We study noncooperative multilateral bargaining games, based on underlying TU games, in which coalitions can renegotiate their agreements. We distinguish between models in which players continue to bargain after implementing agreements ("reversible actions") and models in which players who implement agreements must leave the game ("irreversible actions"). We show that renegotiation always results in formation of the grand coalition if actions are reversible, but that the process may otherwise end with smaller coalitions. On the other hand, we show that the grand coalition cannot form in one step if the core of the game is empty, irrespective of the reversibility of actions.     

Global public goods and coalition formation under matching mechanisms

This paper links coalition theory with matching mechanisms in the presence of global public goods among heterogeneous players. This matching coalition may achieve Pareto‐improving outcomes while avoiding side payments. The paper characterizes conditions of coalition profitability and stability at both interior and corner equilibria. It is generally much harder to satisfy stability conditions than profitability conditions. A matching coalition is more profitable but less stable with a larger matching rate. Empirically there is no stable coalition but this can be overcome by introducing reputation mechanisms. There always exists a stable grand matching coalition if players value their reputation. The matching coalition faces a trade‐off between matching depth and breadth.     

On the stability of coalition structures

We resolve a seeming conflict between a non-existence result on solutions to coalition formation in hedonic games [Barberà, S., Gerber, A., 2007. A note on the impossibility of a satisfactory concept of stability for coalition formation games. Economics Letters 95, 85–90] and the universal existence of stable coalition structures in TU games under the χ-value [Casajus, A., 2008. Outside options, component efficiency, and stability, Games and Economic Behavior (forthcoming). doi: 10.1016/j.geb.2007.04.003].     

The Impact of Resource Uncertainty and Intergroup Conflict on Harvesting in the Common-Pool Resource Experiment

How do resource uncertainty and intergroup conflict affect intragroup cooperation over resources in the common pool dilemmas? Does a danger of sudden resource depletion encourage random acts of violence? There are concerns that climate change will escalate conflicts over, and the scarcity of, renewable resources, which are already under threat or in a state of decline. However, we know surprisingly little about the impact of uncertainty on intergroup conflict over resources. In this paper, we present experimental evidence from a mixed design experiment with two-between-group factors: (1) the presence (or absence) of shocks that can destroy a part of resources; and (2) the availability of intergroup conflict. We find that random shocks encourage resource conservation within groups. The positive impact of resource uncertainty on resource conservation disappears in the presence of conflict. It seems that subjects protect themselves from resource exhaustion in the presence of shocks by engaging in conflict and taking resources from the out-group instead of reducing extraction. In general, conflict promotes intragroup cooperation, but this is conditional on the outcomes of past conflicts. In particular, groups harvest more after wins, and only reduce extraction after losing resources in conflict.     

Natural Resources and Internal Conflict

We present a model of conflict in which each group decides to claim the country’s income and invest in arms or to accept a group neutral allocation of income and not invest in arms. Apart from the usual cooperative or conflictual societies, their strategic choice can result in hierarchically stratified societies in which one group is dominant. We show how the presence and exploitation of certain types of resources matters for the occurrence of conflict or social hierarchical stratification and for the possible effects of trust manipulation. In particular we find that, first, robust (encompassing point and lootable) resource rich economies tend to be conflictual, plantation economies hierarchically stratified and diversified economies cooperative. Second, foreign intervention, aimed at changing the balance of power in the case of conflict, is most effective in robust and diffuse resource rich economies. Third, trust manipulation (as a means to counter conflict) is most effective in subsistence and diffuse resource rich economies. Throughout the article, we cite ample case study and econometric evidence to support our model.     

Barriers to Global Free Trade through Bilateral Agreements

This paper examines the formation of bilateral free trade agreements (FTAs) in the context of a dynamic noncooperative bargaining game with a random proposer. We show that global free trade (a grand coalition) does not necessarily occur unless transfer payments among countries are allowed. When transfer payments are possible, bilateral FTAs always achieve global free trade, but the ex‐ante and ex‐post inequalities of social welfare among countries are larger than those when all countries are independent because of the strategic bargaining behavior.     

Collusion Under Asymmetric Information: The Role of the Correlation

We consider the regulation of a duopoly under incomplete information. When firms act noncooperatively, the regulator uses yardstick mechanisms to bridge his informational gap at no cost. However, this provides the firms with an incentive to collude.
We interpret the correlation as a measure of the congruence/divergence between individual and coalitional incentives. Under positive correlation, these incentives are aligned: the threat of collusion forces the regulator to distort the allocation. Under negative correlation, these incentives are opposed: the regulator can, sometimes, exploit this conflict of interest inside the coalition to eradicate the stakes of collusion at no cost.     

A simple model of coalitional bidding

Summary. We analyze a model of coalitional bidding in which coalitions form endogenously and compete with each other. Since the nature of this competition influences the way in which agents organize themselves into coalitions, our main aim is to characterize the equilibrium coalition structure and the resulting bids. We do so in a simple model in which the seller may have good reason to allow joint bidding. In particular, we study a model in which the agents are budget constrained, and are allowed to form coalitions to pool their finances before engaging in the first price auction. We show that if the budget constraint is very severe, the equilibrium coalition structure consists of two coalitions, one slightly larger than the other; interestingly, it is not the grand coalition. This equilibrium coalition structure is one which yields (approximately) the maximum expected revenue. Thus the seller can induce the optimal (revenue maximizing) degree of cooperation among budget constrained buyers simply by permitting them to collude. Received: June 25, 1999; revised version: November 13, 2000     

The production and cost-sharing of an excludable public good

Summary We study a model of negotiation and coalition formation concerning a public expenditure and its financing. The agents must determine which coalition will jointly produce a public good, how much will be produced, and how the cost is to be shared. Agents that do not belong to the final coalition are excluded from consumption of the public good. Subgame-perfect Nash equilibria in stationary strategies lead to the formation of the grand coalition with an agreed alternative in the core of the economy. Conversely, for each alternative in the core, there exists a subgame-perfect Nash equilibrium in (pure) stationary strategies that leads to the formation of the grand coalition with that alternative.I wish to thank Dieter Balkenborg, Georg Noldeke, Shlomo Weber and Eyal Winter for helpful discussions. The comments of an anonymous referee greatly improved the quality of the exposition. Financial support from Deutsche Forschungsgemeinschaft, SFB 303, is gratefully acknowledged.     

Characterization and incentive compatibility of Walrasian expectations equilibrium in infinite dimensional commodity spaces

Summary. We consider a differential information economy with infinitely many commodities and analyze the veto power of the grand coalition with respect the ability of blocking non-Walrasian expectations equilibrium allocations. We provide two different Walrasian expectations equilibrium equivalence results. First by perturbing the initial endowments in a precise direction we show that an allocation is a Walrasian expectations equilibrium if and only if it is not privately dominated by the grand coalition. The second characterization deals with the fuzzy veto in the sense of Aubin but within a differential information setting. This second equivalence result provides a different characterization for the Walrasian expectations equilibrium and shows that the grand coalition privately blocks in the sense of Aubin any non Walrasian expectations equilibrium allocation with endowment participation rate arbitrarily close to the total initial endowment participation for every individual. Finally, we show that any no free disposal Walrasian expectations equilibria is coalitional Bayesian incentive compatible. Since the deterministic Arrow-Debreu-McKenzie model is a special case of the differential information economy model, one derives new characterizations of the Walrasian equilibria in economies with infinitely many commodities.Received: 29 October 2003, Revised: 24 February 2004, JEL Classification Numbers: D51, D82, D11. Correspondence to: Emma Moreno-GarcíaThe authors are grateful to an anonymous referee for his/her careful reading and helpful comments and suggestions.C. Hervés and E. Moreno acknowledge support by Research Grant BEC2000-1388-C04-01 (Ministerio de Ciencia y Tecnología and FEDER); and support by the Research Grant SA091/02 (Junta de Castilla y León).     

A note on stable and sustainable global tax coordination with Leviathan governments

Itaya et al. (2014) study the conditions for sustainability and stability of capital tax coordination in a repeated game model with tax-revenue maximizing governments. One of their major results is that the grand tax coalition is never stable and sustainable. The purpose of this note is to prove that there are conditions under which the grand tax coalition is stable and sustainable in Itaya et al.'s model.     

DO INSTITUTIONS MITIGATE THE RISK OF NATURAL RESOURCE CONFLICTS?

The resource curse, as manifested by an increased likelihood of conflict over rents, can be mitigated by institutions. Lei and Michaels find that discoveries of “giant” oil fields increase the likelihood of violent conflict, but they find no evidence that democratic institutions mitigate this risk. We test whether institutions mitigate the resource curse by reducing the risk of natural resource conflicts. Our results indicate that high quality economic institutions reduce the likelihood of territorial (separatist) conflicts following natural resource rent windfalls. Highly autocratic and highly democratic institutions also reduce the likelihood of territorial conflict after natural resource rent windfalls. (JEL Q34, O13, P48, D74)