Using willingness to pay to measure the strength of altruistic motives

We introduce a novel experimental procedure to measure altruistic giving along a spectrum, from warm glow to pure altruism, by eliciting willingness to pay to increase the likelihood that a donation is received by a recipient. Whereas previous methods identify pure warm-glow motives, our approach directly measures altruistic preferences and is validated by a survey measure developed by Carpenter (2021). Participants who identify in the survey as altruistic givers are more likely to pay to increase the probability that the donation is implemented and pay more on average than those who identified as mainly motivated by warm glow.