Altruists and envious people who meet in contests are symbionts. They do better than a population of narrowly rational individuals. If there are only altruists and envious individuals, a particular mixture of altruists and envious individuals is evolutionarily stable.

This paper presents a formal theory of reciprocity. Reciprocity means that people reward kind actions and punish unkind ones. The theory takes into account that people evaluate the kindness of an action not only by its consequences but also by the intention underlying this action. The theory...

We present the first causal evidence on the persistent impact of enduring competition on prosociality. Inspired by the literature on tournaments within firms, which shows that competitive compensation schemes reduce cooperation in the short-run, we explore if enduring exposure to a competitive...

The provision of social incentives in the workplace, where performance benefits a charitable cause, has been frequently used in modern organizations. In this paper, we quantify the impact of social incentives on performance under two incentive schemes: piece rate and a winner-take-all...

We show that warm-glow motives in provision by competing suppliers can lead to inefficient charity selection. In these situations, discretionary donor choices can promote efficient charity selection even when provision outcomes are non-verifiable. Government funding arrangements, on the other...

We consider dynamic competition among platforms in a market with network externalities. A platform that dominated the market in the previous period becomes "focal" in the current period, in that agents play the equilibrium in which they adopt the focal platform whenever such equilibrium exists....