Before revision:  Our imputation, in the 2/3-approximate core, implies that a sub-coalition will gain at most a 3/2 factor by seceding, and less in typical cases . We also study the phenomenon of degeneracy in assignment games, i.e., when the maximum weight matching is not unique. We provide insights of an elementary nature gained by studying this phenomenon through the lens of complementary slackness .
After revision:  Our imputation, in the 2/3-approximate core, implies that a sub-coalition will gain at most a 3/2 factor by seceding, and less in typical cases .