  Following the original interpretation of the Shapley value (Shapley, 1953a)
as a priori evaluation of the prospects of a player in a multi-person
interaction situation, we propose a group value, which we call the Shapley
group value, as a priori evaluation of the prospects of a group of players in a
coalitional game when acting as a unit. We study its properties and we give an
axiomatic characterization. Relaying on this valuation we analyze the
profitability of a group. We motivate our proposal by means of some relevant
applications of the Shapley group value, when it is used as an objective
function by a decisionmaker who is trying to identify an optimal group of
agents in a framework in which agents interact and the attained benefit can be
modeled bymeans of a transferable utility game. As an illustrative examplewe
analyze the problem of identifying the set of key agents in a terrorist
network.
