= Convex cooperative game
{title2=$v(S\cup T)+v(S\cap T)\ge v(S)+v(T)$}
A transferable utility game is convex when its coalition-value function is <supermodular>. Equivalently a player's <marginal contribution> cannot decrease when the preceding <coalition> grows. The implication follows by applying the displayed inequality to $A\cup\{i\}$ and $B$ with $A\subseteq B$, $i\notin B$; the reverse implication follows by adding successive marginal inequalities. This property concerns <coalition> values, not geometrical convexity of a strategy space.
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