Given the replacement of cash with cell phone payments, people who are asked to donate to charity can easily promise a donation but delay the transfer until a later date. This may be a way to get out of the ask-situation with a positive image while maintaining the flexibility not to donate. This study explores whether charities can make people keep their promises by making such promises more explicit and more formal.

In a door-to-door fund-raising field experiment, we vary the strength of the promise that donors make. Besides a control group where people can promise to donate, we apply two treatment groups. In the first treatment, donors are asked to verbally pledge a precise amount. In a second treatment, this amount is in addition put on paper with the solicitor’s signature added. Both treatments are aimed at making it morally more expensive not to keep promises. Our results show that: (1) the majority of people do not follow through on their promise to donate; (2) donors who pledge an explicit amount more often keep their promise. The more formal the commitment, the closer the amount donated is to the amount promised; (3) many participants refuse to pledge a donation amount when asked, and those who refuse donate significantly less.