 A public goods game is an n-person Prisoners’ Dilemma. The Pareto optimal outcome is one in which everyone contributes their entire endowment. With \(n = 10\) participants and an endowment of \(x = €10,\) each participant would wind up with \(€20.\) But each individual has an incentive to contribute less. If everyone else contributed their entire endowment, each individual could receive up to \(9*€10*2/10+€10 = €28\) if they contributed nothing. This is the same for everyone in the game, and so the Nash equilibrium strategy is to contribute \(€0,\) resulting in a payoff of \(€10\) for each participant.