The Buy-in Effect: When Increasing Initial Effort Encourages Follow-Through

Behavioral interventions often focus on reducing friction to encourage behavior change. In contrast, we provide evidence that adding initial friction to a sign-up process can increase follow-through behavior. In a field experiment with a state department of transportation ([Formula: see text]), we test whether adding modest friction during sign-up for a carpool platform increases usage. Although a more effortful sign-up process leads to 25% fewer sign-ups, overall usage increases. Importantly, these results were only partly explained by selection: Using an intent-to-treat analysis, participants with a more effortful sign-up process took 1.6 times more carpool trips per week over four months, leading to more overall trips despite fewer users. In a second experiment with online task work, participants with more effortful sign-up were 37% more likely to return the next day and completed more work overall. These results suggest that adding friction may be an overlooked strategy when follow-through, rather than initial uptake, is the primary goal. This paper was accepted by George Wu, behavioral economics and decision analysis. Funding: The authors acknowledge funding from the University of Konstanz for Study 2, Harvard University Pershing Square Foundation for Human Research, and Harvard Business School. The funders had no role in data collection and analysis, the decision to publish, or preparation of this manuscript. Supplemental Material: The online appendices and data files are available at https://doi.org/10.1287/mnsc.2023.03600 .