There is now an extensive literature on "gift exchange" showing that when principals and agents can trade "gifts" (rewards that should not emerge in a competitive equilibrium), exchange becomes more efficient. However, it is not obvious how gift exchange should be organized if the principal's...

Disentangling the motivational drivers of individuals is frequently regarded a key step in reconciling theory and empirical evidence on the voluntary provision of public goods. We present results of a large online field experiments with 12,624 contribution choices by members of the...

There has been little systematic study of the mechanisms typically used to raise money for charity. One of the most common is the simple raffle in which participants purchase chances to win a prize at a constant price. We conduct a field experiment randomly assigning participants to four raffle...

There is a longstanding concern that material rewards might undermine pro-social motivations, thereby leading to a decrease in blood donations. This paper provides an empirical test of how material rewards affect blood donations in a three-month large-scale field experiment and a fifteen-month...