 Unlike the more straightforward generalization, this matrix does reflect, in a highly idealized way, common social choices — between depleting and conserving a scarce resource, between using polluting and non-polluting means of manufacture or disposal, and between participating and not participating in a group effort towards some common goal. When the number of players is small, it represents a version of what has been called the “volunteer dilemma”. A group needs a few volunteers, but each member is better off if others volunteer. (Notice, however, that in a true volunteer dilemma, where only one volunteer is needed, \(n\) is zero and the top right outcome is impossible. Under these conditions \(\bD\) no longer dominates \(\bC\) and the game loses its PD flavor.) A particularly vexing manifestation of this game occurs when a vaccination known to have serious risks is needed to prevent the outbreak of a fatal disease. If enough of her neighbors get the vaccine, each person may be protected without assuming therisks.