Gavan, Malachy

Contact Information

[email protected]

Personal Webpage

Available for interviews at

European Job Market for Economists (EEA)

Allied Social Science Associations (ASSA)

Research interests

Primary: Game Theory and Mechanism Design
Secondary: Negotiation, Agreements, Robust Implementation

Placement Officer

References

Research

"Negotiated Binding Agreements"(Job Market Paper)
I study binding agreements that can result from negotiation, where the agreement is over agents’ behaviour in an underlying strategic environment. The strategic environment is represented by a game. To do so, I propose a negotiation protocol where, in each round of negotiation, agents make public proposals of the action they will take. The protocol terminates when these proposals are confirmed. Confirmation results in a binding agreement and payoffs are that of the agreed action profile. I provide easy-to-check necessary and sufficient conditions for the action profiles that can be agreed to using the solution concept of Negotiated Binding Agreements, a refinement of Subgame Perfect Equilibrium where agents only propose actions they could agree to. A full characterisation of these outcomes is provided for two-player games. I show that these general results are robust to variations in the negotiation procedure including in the timing of proposals, proposing actions for all agents, and the payoff of perpetual disagreement. I show that the necessary and sufficient conditions generalise when coalitions may jointly deviate in a cooperative way and are consistent with perturbed versions of the β-core.

“Safe Implementation" (with A. Penta)
We introduce Safe Implementation, a notion of implementation that adds to the standard requirements the restriction that deviations from the baseline solution concept induce outcomes that are acceptable. The primitives of Safe Implementation therefore include both a Social Choice Correspondence, as standard, and an Acceptability Correspondence, each mapping every state of the world to a subset of allocations. This framework generalizes standard notions of implementation, and can accommodate a variety of considerations, including robustness concerns with respect to mistakes in play, model misspecification, behavioral considerations, state-dependent feasibility restrictions, limited commitment, etc. We provide results both for general solution concepts and for the case in which agents’ interaction is modelled by Nash Equilibrium. In the later case, we identify necessary and sufficient conditions (namely, Comonotonicity and safety-no veto) that restrict the joint behavior of the Social Choice and Acceptability Correspondences. These conditions are more stringent than Maskin’s (1978), but coincide with them when the safety requirements are vacuous. We also show that these conditions are quite permissive in important economic applications, such as environments with single-crossing preferences and in problems of efficient allocation of indivisible goods, but also that Safe Implementation can be very demanding in environments with ‘rich’ preferences, regardless of the underlying solution concept.

"Existence of Weak Coalitional Equilibrium: Allowing for Overlapping Coalitions"
In this paper, I show the methodological advantage of taking the notion of “an improvement for a group” to mean that there is a joint action of the group that induces a strict improvement in utility for all its members. This is opposed to assuming that no agent in the group is worse off while one is strictly better off. To do so, I show that the sufficient conditions of Ray and Vohra (1997)’s Coalitional Equilibrium can be weakened when this interpretation is taken. I do so by showing that, taking the interpretation that no joint deviation induces a strict improvement for all agents, the existence of Coalitional Equilibrium is implied by the existence of a Nash equilibrium of an auxiliary game. Further to this, I show that the proof of existence can be extended to a generalisation of the concept, where groups may overlap but do not necessarily include the grand coalition. This allows for coalition configurations to be taken from a specific set of covers, while still ensuring existence. This provides the first step in answering the question of the existence of solution concepts with overlapping coalitions, while a deviation of the grand coalition is not permitteed.

Research in Progress

"Efficient Tariff under Strategic Side Payments" (with M. Ptashkina)

"Grand Coalition Rationalizability and Undominated Correlated Equilibria" (with P. Ennuschat)