On coalition formation: Durable coalition structures

We define a solution to the problem of coalition formation that applies to purely hedonic games. Coalition structures satisfying our requirements are called durable, and we interpret them as much more likely to last than those coalition structures not satisfying the requirements, which we call transient. Durability results from a combination of foresight and extreme risk aversion on the part of agents, when considering to join others to disrupt an existing structure in search of higher gains. Agents' calculations are also constrained to satisfy a strong consistency requirement, which is reflected in the recursive structure of our definition. We prove that durable coalition structures always exist, and we provide examples of hedonic games where our solutions apply nicely. © Elsevier Science B.V. All rights reserved.