In this paper, we introduce axiomatically a new value for cooperative
TU games satisfying the efficiency, additivity, and symmetry axioms of
Shapley (1953) and some new postulate connected with the average marg
inal contributions of the members of coalitions which can form. Our so
lution is referred to as the solidarity value. The reason is that its
interpretation can be based on the assumption that if a coalition, say
S, forms, then the players who contribute to S more than the average
marginal contribution of a member of S support in some sense their ''w
eaker'' partners in S. Sometimes, it happens that the solidarity value
belongs to the core of a game while the Shapley value does not.