involving a commitment. The hypothesis is tested in a large-scale field experiment on blood donations. We find that this “active …

social distances, but only one of these decisions is implemented. We decompose altruistic preferences into baseline altruism … towards strangers, and directed altruism towards friends. In order to separate the motives that are altruistic from the ones … that decision-makers vary widely in their baseline altruism, but pass at least 50 percent more surplus to friends as …

blood donations rather than an increase. This paper provides an empirical test of how material incentives affect blood … donations in a large-scale field experiment spanning three months and involving more than 10,000 previous donors. We examine two … types of incentive: a lottery ticket and a free cholesterol test. Lottery tickets significantly increase donations, in …

results, yet it is straightforward enough to be used in many applied situations where altruism, or a baser motive, is implied. …