ICES Experimental Economics Brown Bag Lecture
A Natural Experiment on Gift Exchange
Thursday, September 25, 2025 12:00 PM to 1:00 PM EDT
Vernon Smith Hall (formerly Metropolitan Building), Room 5075
The Interdisciplinary Center for Economic Science (ICES) presents an ICES Brown Bag Lecture featuring:
University of Exeter
A Natural Experiment on Gift Exchange
Abstract
We examine a large scale, natural field experiment in gift exchange within a gig economy firm operating in the food delivery market. The firm rewarded over 30,000 riders in 10 countries with gifts of $275, $690, $1,380, and $13,800, depending on past performance. We track riders’ daily behavior over 27 months across 10 countries. Using a difference-in-differences approach, we find no effect on hours worked or orders delivered in the month following the gift announcement (but pre-payment) relative to a random sample of unrewarded riders. We find a significant negative effect post-payment. The net effect over 18 months post-gift is negative and substantial: rewarded riders deliver fewer orders, work fewer hours and are more likely to quit the platform than unrewarded riders. A regression discontinuity analysis indicates no evidence of social comparisons between reward levels, suggesting that negative reciprocity and income effects are driving riders’ responses to the gift program.
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