The Voice of the Emperor and Personalized Messages during the COVID-19 Pandemic

Last registered on June 18, 2024


Trial Information

General Information

The Voice of the Emperor and Personalized Messages during the COVID-19 Pandemic
Initial registration date
April 27, 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
April 27, 2020, 11:34 AM EDT

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

Last updated
June 18, 2024, 3:15 AM EDT

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



Primary Investigator

Osaka University

Other Primary Investigator(s)

PI Affiliation
Kindai University

Additional Trial Information

Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
The COVID-19 pandemic has threatened many human lives and economic activities in the world. Governments worldwide took several measures to prevent the spread of coronavirus including law-, military-, and/or technology-enforced lock-downs. However, not all the governments immediately took such ``hard" measures, but some, such as Sweden and Japan, took ``soft" measures, e.g., providing political messages to citizens so that they take self-restraint actions on their own.

Despite the flood of administrative messages asking for self-restraint of leaving home, and the emergency declaration by the government on April the 7th, since there are no practical fines against the violations, there are some people who would not comply. This situation has become a social issue and has revealed how difficult it is for a government to guide citizens by providing advisory messages even though the whole society obviously benefits in the long run by following them.

With this circumstance in Japan, this study conducts a Randomized Controlled Trial experiment to investigate causal effects of information provisions to individuals on their self-restraint behaviors with consideration of two novel features in our messages. The first feature we test is the power of the Royals over the political authority. The second one to be examined is the power of personalized messages over commonly shared slogans. We will test if those new features could enhance self-restraint behaviors among Japanese citizens.
External Link(s)

Registration Citation

Kitamura, Shuhei and Katsunori Yamada. 2024. "The Voice of the Emperor and Personalized Messages during the COVID-19 Pandemic." AEA RCT Registry. June 18.
Experimental Details


We conduct randomized information manipulations, exploiting a 2-by-2 factorial design. It is a three week online panel survey for around 3,500 subjects in Japan.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
1. hours of outings
2. hours of outings for unnecessary purposes
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Intentions of outings
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
We conduct randomized information manipulations, exploiting a 2-by-2 factorial design.

First, we have two conditions regarding the sender of the messages on self-restraint behaviors. Specifically, we consider the political authority (the current prime minister) and the current Emperor as the ones who send messages. Since there is already a flood of administrative messages on staying home at the time of the experiment, we consider the condition of the political authority to be our control group. In Japan, the Imperial Family is well-respected and is supposed to be the ``symbol" of Japan. As such, even without any political power with him, the Emperor can influence the society with his messages. Therefore, we will treat this condition as our treatment, and test the symbolic power of the Royals.

In both cases, the senders of messages hope that the society will overcome the COVID-19 pandemic. For the sake of the salience of the experiment, we choose actual statements made by either sender before our experiment set off, rather than we make up fictional messages. Those messages come with drawing images of the senders in order to enhance the reality of the messages.

Next, we have two conditions regarding personalized messages. If participants are in ``NO" condition, they will receive some common information for everybody, just as it is happening in the real world. Instead, if participants are in ``Yes" condition, they will receive personalized messages. Those personalized messages contain information of their own hours of outings from the previous week, together with the median value of outing hours for the rest of participants. As such, from the messages it is easy for our participants to grasp where they stand in the distributions of outing hours. The aim of our personalized massages is to make the information in the society more salient to individuals, thereby promoting responsible behaviors on their own.
Experimental Design Details
Randomization Method
Randomization done in office by a computer
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
3,500 individuals
Sample size: planned number of observations
3,500 individuals
Sample size (or number of clusters) by treatment arms
875 individuals per arm
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
When the group size is 875, power is 0.8, and the false discovery rate is 0.05, the minimum detectable effect between a pair of groups is 0.1897 standard deviations.

Institutional Review Boards (IRBs)

IRB Name
Institutional Review Board of Faculty of Economics, Kindai University
IRB Approval Date
IRB Approval Number
Analysis Plan

Analysis Plan Documents

Pre-Analysis Plan

MD5: bb196e796916e913e6a0dca1e7d025b9

SHA1: c6e594146bc6b82f4c6f2ab765eef90079411a1c

Uploaded At: April 27, 2020


Post Trial Information

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Is the intervention completed?
Intervention Completion Date
April 24, 2020, 12:00 +00:00
Data Collection Complete
Data Collection Completion Date
May 04, 2020, 12:00 +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
Was attrition correlated with treatment status?
Final Sample Size: Total Number of Observations
Final Sample Size (or Number of Clusters) by Treatment Arms
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

A randomized survey experiment (N = 2,868) was conducted at the onset of the COVID-19 pandemic to examine the effects of information provision on individuals’ cooperation with stay-home activities. Employing a 2 × 2 factorial design, the study examined the influence of social comparison and a powerful messenger. Using an online sample of approximately 3,000 Japanese respondents, it was found that participants demonstrated greater cooperation with stay-home activities when they perceived that they had spent a relatively long time outside the home compared with prevailing social norms in the previous week. Conversely, individuals who spent a relatively short time outside the home exhibited the opposite effect. However, these results were observed solely in conjunction with the influence of a powerful messenger. The study also explored heterogeneous responses based on personality traits. In conclusion, the results highlight the challenges of changing behavior through informational interventions, emphasizing the role of both the characteristics of the sender and recipient of the information.
Kitamura, S. and K. Yamada (2023). The constructive and destructive power of social norms in the presence of authoritative influence. American Psychologist.

Reports & Other Materials