How Can Bill and Melinda Gates Increase Other People's Donations to Fund Public Goods?

We conducted a fundraising experiment with an international development nonprofit organisation in which a matching grant offered by the Bill and Melinda Gates Foundation raised more funds than from an anonymous donor. The effect is strongest for solicitees who previously gave to other BMGF-supported, poverty charities. With supporting evidence from two other fundraising experiments as well as a survey experiment, we argue this is consistent with a quality signal mechanism. Alternative mechanisms are discussed, and not ruled out. The results help inform theories about charitable giving decision-making, and provide guidance to organisations and large donors on how to overcome information asymmetries hindering fundraising.