Uniqueness of Coalitional Equilibria

We provide an existence and a uniqueness result for coalitional equilibria of a game in strategic form. Both results are illustrated for a public good game and a homogeneous Cournot-oligopoly game.Existence and uniqueness of coalitional equilibrium, Game in strategic form

Dynamic Effects on the Stability of International Environmental Agreements

In terms of the number of signatories, one observes both large and small international environmental agreements. The theoretical literature, based on game theory, discusses different concepts and mechanisms for the stability of coalitions and has reached the conclusion that, under farsightedness, both large and small stable coalitions can occur. In the context of a repeated game, this implies that large stable coalitions can also be sustained over time by a simple trigger mechanism, for large enough discount factors. However, if changes in time implement changes in state, this conclusion does not hold anymore: only small stable coalitions can be sustained.IEA’s, Coalitional stability, Dynamics

Optimal Transfers and Participation Decisions in International Environmental Agreements

The literature on international environmental agreements has recognized the role transfers play in encouraging participation in international environmental agreements (IEAs), but the few results achieved so far are overly specific and do not exploit the full potential of transfers for successful treaty-making. Therefore, in this paper, we develop a framework that enables us to study the role of transfers in a more systematic way. We propose a design for transfers using both internal and external financial resources and making “welfare optimal agreements” self-enforcing. To illustrate the relevance of our transfer scheme for actual treaty-making, we use a well-known integrated assessment model of climate change to show how appropriate transfers may be able to induce almost all countries into signing a self-enforcing climate treaty.Self-enforcing international environmental agreements, Climate policy, Transfers

Bargaining with Non-Monolithic Players

This paper analyses strategic bargaining in negotiations between non-monolithic players, i.e. agents starting negotiations can split up in smaller entities during the bargaining process. We show that the possibility of scission in the informed coalition implies that it loses its information advantages. We also show that when the possibility of a scission exists the uninformed player does not focus on his or her beliefs about the strength of the informed coalition but on the proportion of weak/strong players within this coalition. Finally, our results show that the possibility of a scission reduces the incentives for the leader to propose a high offer to ensure a global agreement. We apply this framework to international negotiations on global public goods and to wage negotiations.Strategic bargaining, Non-monolithic players, Scission, Noncooperative game-theory

Pairwise-Stability and Nash Equilibria in Network Formation

Suppose that individual payoffs depend on the network connecting them. Consider the following simultaneous move game of network formation: players announce independently the links they wish to form, and links are formed only under mutual consent. We provide necessary and sufficient conditions on the network link marginal payoffs such that the set of pairwise stable, pairwise-Nash and proper equilibrium networks coincide, where pairwise stable networks are robust to one-link deviations, while pairwise-Nash networks are robust to one-link creation but multi-link severance. Under these conditions, proper equilibria in pure strategies are fully characterized by one-link deviation checks.Network formation, Pairwise-stability, Proper equilibrium

Strategic Basins of Attraction, the Farsighted Core, and Network Formation Games

We make four main contributions to the theory of network formation. (1) The problem of network formation with farsighted agents can be formulated as an abstract network formation game. (2) In any farsighted network formation game the feasible set of networks contains a unique, finite, disjoint collection of nonempty subsets having the property that each subset forms a strategic basin of attraction. These basins of attraction contain all the networks that are likely to emerge and persist if individuals behave farsightedly in playing the network formation game. (3) A von Neumann Morgenstern stable set of the farsighted network formation game is constructed by selecting one network from each basin of attraction. We refer to any such von Neumann-Morgenstern stable set as a farsighted basis. (4) The core of the farsighted network formation game is constructed by selecting one network from each basin of attraction containing a single network. We call this notion of the core, the farsighted core. We conclude that the farsighted core is nonempty if and only if there exists at least one farsighted basin of attraction containing a single network. To relate our three equilibrium and stability notions (basins of attraction, farsighted basis, and farsighted core) to recent work by Jackson and Wolinsky (1996), we define a notion of pairwise stability similar to the Jackson-Wolinsky notion and we show that the farsighted core is contained in the set of pairwise stable networks. Finally, we introduce, via an example, competitive contracting networks and highlight how the analysis of these networks requires the new features of our network formation model.Basins of attraction, Network formation, Supernetworks, Farsighted core, Nash networks

The Egalitarian Sharing Rule in Provision of Public Projects

In this note we consider a society that partitions itself into disjoint jurisdictions, each choosing a location of its public project and a taxation scheme to finance it. The set of public project is multi-dimensional, and their costs could vary from jurisdiction to jurisdiction. We impose two principles, egalitarianism, that requires the equalization of the total cost for all agents in the same jurisdiction, and efficiency, that implies the minimization of the aggregate total cost within jurisdiction. We show that these two principles always yield a core-stable partition but a Nash stable partition may fail to exist.Jurisdictions, Stable partitions, Public projects, Egalitarianism

Tinbergen and Theil Meet Nash: Controllability in Policy Games

This paper generalizes the classical theory of economic policy to a static LQ-strategic context between n players. We show how this generalized version of controllability can profitably be used to deal with policy ineffectiveness issues and Nash equilibrium existence.Policy games, policy ineffectiveness, static controllability, Nash equilibrium existence

The Pigouvian Tax Rule in the Presence of an Eco-Industry

Pollution abatement goods and services are now largely being delivered by a specialized “eco-industry.” This note reconsiders Pigouvian taxes in this context. We find that the optimal emission tax will depart from the marginal social cost of pollution according to the polluters’ and the environment firms’ relative market power.Pigouvian taxes, Environment industry