The impact of a pledge campaign and the promise of publicity on charitable giving: a randomised controlled trial of a book donation campaign

IntroductionCharities and public organisations can potentially enhance donations of time, money or goods by framing their demands to be persuasive to citizens. One such approach is to ask for a pledge, drawing on theory from psychology which suggests that if people make a commitment to do something they face strong internal and societal pressure to behave in a way that is consistent with their promise (Bator and Cialdini, 2000: 536). Another approach is to offer public recognition of the donation, assuming that people are motivated by social approval (Ariely et al 2009: 544). MethodsWe report here a randomised controlled trial to test the effectiveness of asking for a pledge and offering public recognition. Letters were sent to 11,812 households in Manchester asking them to donate a book for school libraries in South Africa. Households were randomly assigned to one of 3 groups of equal size: one treatment group were asked to pledge to donate a book; a second treatment group were asked to pledge and were also told that a list of book donors would be displayed locally. A control group were sent similar information about the book collection, but without the pledge or the offer of publicity.ResultsAsking people to pledge and offering public recognition attracted book donations from 9 per cent of households, compared to 7 per cent in a control group, an effect size of 22 per cent (p