Why Larger Signatures on Solicitation Letters Increase Donations

Donation solicitation letters contain a signature block featuring the personal signature and name of the individual endorsing the letter. In three studies, we find that the size of the personal signature appearing in the signature block predictably affects donor responses to solicitation letters, with larger signatures generating bigger donations. We first observe this effect in a large-scale field experiment conducted with a hospital foundation: for the identical solicitation letter, increasing the sender's signature size generated nearly 100% more donation revenue. In two laboratory experiments, we find that individuals who receive a letter with a larger personal signature are willing to donate more because they believe the organization will have a greater impact. We discuss theoretical contributions to our understanding of identity symbols and practical implications for non-profit organizations.