Identity and equal treatment in negative externality agreements

This paper examines the interaction of two types of provisions in international environmental agreements: an identity-based minimum participation clause (MPC) and an equal treatment provision. While MPCs have been widely studied in the context of multilateral agreements, this paper is the first to formally introduce treaties specifying equal proportional reductions from the no-treaty equilibrium for all participants. Does the presence of these two provisions assist or impede the formation and efficiency of the grand coalition? In cases of equal treatment and heterogeneity of agents, smaller coalitions may result in higher welfare than requiring the grand coalition. Using game theoretic analysis of a set of games, this paper gives a set of sufficient conditions for this welfare result to hold in a one-shot negative externality coalition game and presents examples of when smaller agreements do, and do not, improve upon unanimity. Furthermore, this paper focuses on how the choice of negotiation rules affects the optimal set of signatories. By specifying equal treatment (e.g. a proportional reduction rule) in a treaty, gains to the “narrow but deep” approach may warrant a smaller coalition.