 This payoff structure is identical to a Prisoner’s Dilemma and illustrates the free-rider problem. Bob prefers the public good to be produced but since he benefits from it whether or not he contributes, his most preferred alternative is that in which Sally pays for its production and he free rides on her contribution. Sally faces identical payoffs. Therefore, both will choose not to contribute, meaning that the public good will not be produced, even though the alternative outcome in which both contribute would be Pareto superior. A Pareto-superior outcome is one that makes at least one individual better off while making no-one worse off. (Contribute; Contribute) is Pareto-superior to (Don’t contribute; Don’t contribute). (Don’t contribute; Don’t contribute) is the equilibrium strategy (in the sense that no player has a reason to deviate from playing it, given the other player’s move) but at the same time there is an outcome both would prefer if it could be reached, namely, (Contribute; Contribute).