Opt-in or Opt-out for Walking Incentive: Evidence from a Field Experiment

Last registered on March 27, 2021


Trial Information

General Information

Opt-in or Opt-out for Walking Incentive: Evidence from a Field Experiment
Initial registration date
December 21, 2020

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
December 22, 2020, 11:46 AM EST

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Last updated
March 27, 2021, 9:38 PM EDT

Last updated is the most recent time when changes to the trial's registration were published.



Primary Investigator

University of Hyogo

Other Primary Investigator(s)

PI Affiliation
Tohoku Gakuin University

Additional Trial Information

On going
Start date
End date
Secondary IDs
We study the impact of financial incentive and its schemes on physical activity, or walking behavior. When receiving incentive, some people are motivated to increase their walking steps, while others may decrease them because of motivational crowding out. This study introduces two type of self-selective incentive schemes, opt-in and opt-out. Under the opt-in scheme, incentive is not provided by default, and people need to make a registration if they need it. In contrast, under the opt-out scheme, incentive is provided by default, and people need to cancel the incentive enrollment if they do not need it. We evaluate the average treatment effect of the two schemes on walking behavior, and investigate which scheme is more effective for providing incentive to the people who increase their steps by receiving the incentive.
External Link(s)

Registration Citation

Kurokawa, Hirofumi and Shusaku Sasaki. 2021. "Opt-in or Opt-out for Walking Incentive: Evidence from a Field Experiment." AEA RCT Registry. March 27. https://doi.org/10.1257/rct.6964
Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Steps per day
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
We randomly assign individuals to a control group or to one of two different treatment groups, which receive an incentive intervention.
Experimental Design Details
This experiment includes totally four phases (8 weeks) with one phase of 2 weeks. In the first phase, no intervention is given to any group. In the second phase, the two treatment groups have an option to receive financial incentive. Specifically, people in the groups can receive 5 yen for every 1000 steps taken per day. However, people in the opt-in group need to make a registration if they need the incentive. On the other hand, people in the opt-out group need to cancel the incentive enrollment if they do not need the incentive. The third and fourth phases are periods for follow-up. In the fourth phase, in terms of fairness, incentive is provided to people in the control group, but they can cancel it as similarly with those in the opt-out.
Randomization Method
Stratified Randomization done by a computer. The strata are based on baseline steps per day and needs of incentive.
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
700 individuals (at maximum).
Sample size: planned number of observations
235 individuals in the opt-in group, 235 individuals in the opt-out group, and 235 individuals in the control group (respectively at maximum).
Sample size (or number of clusters) by treatment arms
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
IRB for Kobe City Health Services
IRB Approval Date
IRB Approval Number
IRB Name
School of Economics and Management, University of Hyogo IRB
IRB Approval Date
IRB Approval Number


Post Trial Information

Study Withdrawal

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Is the intervention completed?
Data Collection Complete
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials