Alliances and negotiations

Negotiations often occur not between individuals but among groups (companies, trade unions, political parties, etc.) each representing composite interests, whose bargaining behaviour is regulated by some collective decision mechanism. In this paper we provide a natural model of such circumstances. We formalise the notion of 'alliance' and show how different preference aggregation procedures within the alliance affect the bargaining outcome. In particular, we find that unanimity procedures lead to 'more aggressive' negotiating tactics than majority procedures.