 Imputation in a coalitional game

An imputation is an efficient, individually rational allocation in a transferable utility game. Its total is the grand-coalition value and each player receives at least its singleton value. The set is nonempty exactly when $v(N)\ge {\sum }_{i}v(\{i\})$, and is then compact. This individual-rationality condition distinguishes the nucleolus from the prenucleolus.