For a simple cooperative game, the Shapley value is the probability that a player is pivotal in a uniformly random ordering. Symmetry gives one value for permanent members and another for nonpermanent members.
A particular nonpermanent member is pivotal exactly when all five permanent members and exactly three of the other nine nonpermanent members precede them. The predecessor set then has size eight. There are such sets, each giving orderings. Their Shapley value is therefore
Every ordering has exactly one pivotal member, since the empty coalition loses and the full coalition wins. This proves efficiency directly: , where is the value of each permanent member. Hence
The vector has five entries and ten entries . As a check, a permanent member is pivotal when they are last among the permanent members and occupy a position from nine to fifteen; counting those orderings gives the same .
Shapley value 2026-10-06
The Shapley value averages each player's marginal contribution over uniformly random player orderings. Exactly orderings have immediately before player , giving the formula. The values sum to by telescoping each ordering. In a simple cooperative game this is the probability of being pivotal. For a convex cooperative game, Shapley value belongs to the core of a convex game guarantees a stable allocation as well.
Transferable utility game 2026-10-06
A finite transferable utility game gives each coalition a real value that its members can distribute among themselves. The usual normalization is . An efficient payoff vector satisfies . Simple cooperative games model winning coalitions with values zero and one; convex cooperative games model increasing marginal contributions.
Weighted voting game 2026-10-06
A weighted voting game assigns player weights and a threshold, and declares coalitions winning when their total weight passes that threshold. The strict convention is equivalent to quota for integer weights; another common convention writes a weak inequality directly. Nontrivial examples are simple cooperative games. Having nonnegative weights does not guarantee a convex cooperative game: two-of-three majority supplies a counterexample.