Why Do People Volunteer? An Experimental Analysis of Preferences for Time Donations∗

Why do individuals volunteer their time even when recipients receive far less value than the donor’s opportunity cost? Previous models of altruism that focus on the overall impact of a gift cannot rationalize this behavior, despite its prevalence. We develop a model that relaxes this assumption, allowing for differential warm glow depending on the form of the donation. In a series of laboratory experiments that control for other aspects of volunteering, such as its signaling value, subjects demonstrate behavior consistent with the theoretical assumption that gifts of time produce greater utility than the same transfers in the form of money. Subjects perform an effort task, accruing earnings at potentially different wage rates for themselves or a charity of their choice, with the ability to transfer any of their personal earnings to charity at the end of the experiment. Subjects exhibit strong preferences for donating time even when differential wage rates make it costly to do so. The results provide new insights on the nature of volunteering and gift-giving.