 Other norms such as “everyone should do their bit” or fairness and equality norms can also help to increase private contributions to public goods. People might simply think that it is morally wrong to free ride (Sugden 1984). Social norms can motivate people to act altruistically but also help to solve co-ordination problems by specifying property rights and the terms of contracts (Young 1998). Clean streets (the absence of littering) can be regarded as a public good, and let us assume that littering isn’t punishable by law. In a game-theoretic setting, individuals would be expected to underproduce the public good, i.e., to litter too much. A norm not to litter can now help to induce people to co-operate and play the non-Nash equilibrium but Pareto superior strategy. The punishment of norm-violators through social sanctions will help to make people follow the norm without the government having to police norm following.