How Does Opt-in Work? A Field Experiment on Financial Incentives for Physical Activity

We examined the effectiveness of two different schemes for providing financial incentives to promote physical activity. We collaborated with a local government in Japan to conduct a field experiment with 498 residents randomly assigned to participate in one of three groups: an “opt-in†group (needed to apply to receive the incentive based on their daily steps), an “opt-out†group (received the incentive by default, but could request not to receive it), and a control group (no incentive). In the opt-in group, 31.1% of the participants applied to receive the incentive, while 100% of those in the opt-out group retained the default option and received it, indicating that their take-up rates depended heavily on the default settings. Our estimation results suggest that providing financial incentives in the opt-in scheme can be effective and efficient. The opt-in group, overall, showed a statistically significant increase of approximately 710 steps per day during the first half of the treatment period, and the number of steps was estimated to increase by 2,280 among the 31.1% of participants who opted-in to receive the incentive. The opt-out scheme did not show any significant increase in their number of daily steps.