Understanding the coincidence of allocation rules: symmetry and orthogonality in TU-games

The main goal of this paper is to understand the reasons driving the coincidence of different allocation rules for different classes of games. We define a new symmetry property, reverse symmetry, and study its geometric and game theoretic implications. In particular, we show that most classic allocation rules satisfy it. Then, we introduce and study a notion of orthogonality between TU-games, which allows to establish a restricted additivity property for the nucleolus. Also, in our analysis we identify different classes of games for which all allocation rules satisfying some sets of basic properties coincide. These properties are satisfied, among others, by the Shapley value and the nucleolus. Copyright Springer-Verlag Berlin Heidelberg 2014