Rewarding Altruism? A Natural Field Experiment
We present evidence from a natural field experiment involving nearly 100,000 individuals on the effects of offering economic incentives for blood donations. Subjects who were offered economic rewards to donate blood were more likely to donate, and more so the higher the value of the rewards. They were also more likely to attract others to donate, spatially alter the location of their donations towards the drives offering rewards, and modify their temporal donation schedule leading to a short-term reduction in donations immediately after the reward offer was removed. Although offering economic incentives, combining all of these effects, positively and significantly increased donations, ignoring individuals who took additional actions beyond donating to get others to donate would have led to an under-estimate of the total effect, whereas ignoring the spatial effect would have led to an over-estimate of the total effect. We also find that individuals who received a reward by surprise were less likely to donate after the intervention than subjects who received no reward, suggesting that for some individuals a surprise reward adversely affected their intrinsic motivations. We discuss the implications of these findings for understanding pro-social behavior.
We are extremely thankful to the CEO, Board members, and staff of the Northern Ohio Blood Service Region of the American Red Cross, and, in particular, to Brent Bertram and Barbara Thiel for their invaluable assistance and collaboration. We thank the participants at the Advances with Field Experiments workshops in Philadelphia and Chicago, the ASHE conference in Ithaca, the ASSA meetings in Denver, the Midwest Health Economics Conference in Ann Arbor, the 7th annual SITE workshop in Experimental Economics, the Southern Ontario Behavioral Decision Research Conference in Toronto, the Workshop on Natural Experiments and Controlled Field Studies in Munich, and at seminars at Case Western Reserve University, EIEF, Johns Hopkins University, Melbourne University, Monash University, Queensland University of Technology, the University of Michigan, the University of New South Wales, the University of Queensland, UC San Diego, UC Santa Barbara, the University of Toronto, and Yale University for their comments. We benefited from conversations with Christian Catalini, Ray Fisman, Alberto Galasso, Uri Gneezy, Sacha Kapoor, Steve Leider, Liz Lyons, Costas Meghir, Philip Oreopoulos, Devin Pope, Joseph Price, Heather Royer and Justin Sydnor. Soujanya Bulagannawar, Tina Chen, Il Myoung Hwang, Sebastian Maass, Dominic Smith, Sarah Stith and Andrew Zhang provided outstanding research assistance. Financial support from the National Science Foundation (Grants #0851587 and #0851602) is gratefully acknowledged. The views expressed herein are those of the authors and do not necessarily reflect the views of the National Bureau of Economic Research.
"Rewarding Volunteers: A Field Experiment," Management Science, 60(5), 1107–1129, 2014