An Almost Ideal Sharing Scheme for Coalition Games with Externalities

Cooperative agreements among firms to coordinate R&D investments and share knowledge or coordination among nations to reduce trade barriers or to provide global public goods usually proves difficult due to free-rider incentives. In this paper, we propose a sharing scheme for the distribution of the gains from cooperation for games with externalities and heterogeneous players in order to mitigate free-rider problems. We show that every sharing rule belonging to our scheme leads to the same set of stable coalitions which is never empty. This scheme is "almost ideal" because it stabilizes those coalitions generating the highest possible global worth among the set of all "potentially stable coalitions". Our Almost Ideal Sharing Scheme is particularly powerful for economic problems where outsiders benefit from the coalition's actions (positive externalities) and which therefore are likely to suffer from severe free-riding.