Are cooperators efficiency- or fair-minded?Evidence from a public goods experiment

We use a two-person public goods experiment to distinguish betweene±ciency and fairness as possible motivations for cooperative behavior.Asymmetric marginal per capita returns allow only the high-productivityplayer to increase group payo®s when contributing positive amounts. Asymmetriccontributions, however, yield unequal individual payo®s. To assessa priori cooperative preferences, we measure individual `value-orientations'by means of the decomposed game technique. Overall, our results indicatethat fairness (or inequality aversion) is more in°uential than e±ciency indriving behavior.