Smith 提到了 OPM (other person’s money) 問題，可以用以下的方式解決
We could give the constant positive sum ultimatum game economic content as follows: Each player provides $M of his own money. Some procedure is used for pairing the subjects, and determining who is to be Player 1 and who Player 2; this procedure in some variations might incorporate an earned and/or investment feature. It is understood that their pairing has economic significance in the sense that there are synergistic gains from the interaction equal to some fixed sum y > 2M. The experimenter provides only the surplus above 2M which represents the gains from specialization and exchange, as this is the one reliable source of a “free lunch” that converts economic systems into non-zero sum games. Hence, the total to be shared under the property right rules of the game is 2M + y, making it feasible for each to receive a share of the jointly created net gain above their pooled initial contribution, 2M.