loops where vindictive acts are met with further vindictive acts. In practice, despite the neat logic of standard neoclassical models, these kinds of sociological models do impinge upon very many economic relations, though in different ways and to different degrees. For example, if an employee has been exceptionally loyal, a manager may feel some obligation to treat that employee well, even when it is not in his (narrowly defined, economic) self-interest to do so. It would appear that although broader, longer-term economic benefits may result (e.g. through reputation, or perhaps through simplified decision-making according to fairness norms), a major factor must be that there are noneconomic benefits the manager receives, such as not having a guilty conscience (loss of self-esteem). For real-world, socialised, normal human beings (as opposed to abstracted factors of production), this is likely to be the case quite often. (As a quantitative estimate of the importance of this, Weisbrod's 1988 estimate of the total value of voluntary labor in the US - $74 billion annually – will suffice.) Examples of the negative aspect of fairness include consumers "boycotting" firms they disapprove of by not buying products they otherwise would (and therefore settling for second-best); and employees sabotaging firms they feel hard done by. Rabin (1993) offers three stylised facts as a starting-point on how norms affect behaviour: (a) people are prepared to sacrifice their own material well-being to help those who are being kind; (b) they are also prepared to do this to punish those being unkind; (c) both (a) and (b) have a greater effect on behaviour as the material cost of sacrificing (in relative rather than absolute terms) becomes smaller. Rabin supports his Fact A by Dawes and Thaler's (1988) survey of the experimental literature, which concludes that, for most one-shot public good decisions in which the individually optimal contribution is close to 0%, the contribution rate ranges from 40 to 60% of the socially optimal level. Fact B is demonstrated by the "ultimatum game" (e.g. Thaler 1988), where an amount of money is split between two people, one proposing a division, the other accepting or rejecting (where rejection means both get nothing). Rationally, the proposer should offer no more than a penny, and the decider accept any offer of at least a penny, but in practice, even in one-shot settings, proposers make fair proposals, and deciders are prepared to punish unfair offers by rejecting