 A third reason for the ability of public goods to be provided privately to be discussed here is the existence of social norms. For example, as long as individuals meet repeatedly to decide about the creation of a public good, they might realise that lying is self-destructive, and as the situation is iterated, it is possible that a norm of truthful revelation of the valuations is developed upon which a convention of telling the truth would be built (Taylor 1976; Schotter 1981). That a non-co-operative strategy is not necessarily optimal in repeated games is a well-known result in game theory (see entry on  game theory, section on repeated games and coordination).