Follow-up Study

Last registered on June 21, 2024


Trial Information

General Information

Follow-up Study
Initial registration date
July 03, 2018

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
July 05, 2018, 7:36 PM EDT

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

Last updated
June 21, 2024, 6:02 AM EDT

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



Primary Investigator

Bocconi University

Other Primary Investigator(s)

PI Affiliation
University of Münster

Additional Trial Information

Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
We run a follow-up study for the registered field experiment "The Welfare Effects of Information Nudges - Evidence from a Natural Field Experiment" (RCT ID: AEARCTR-0002814). In a brief 3-question survey we test how our different informational treatments have affected consumer beliefs and whether the change in beliefs is associated with a change in purchasing behavior.
External Link(s)

Registration Citation

Rodemeier, Matthias and Andreas Löschel. 2024. "Follow-up Study ." AEA RCT Registry. June 21.
Former Citation
Rodemeier, Matthias and Andreas Löschel. 2024. "Follow-up Study ." AEA RCT Registry. June 21.
Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Subject's belief about how much a 4W LED light bulb saves in annual electricity costs compared to a 40W incandescent light bulb.
Self-reported electricity price of the subject.
Self-reported number of hours a subject uses a light bulb on average.
The number of LED, CFL, halogen and incandescent light bulbs purchased.
The average energy efficiency level (wattage) of the products purchased.
The price elasticity for all four light bulb technologies (incandescent, halogen, CFL, LED).
The probability of purchasing.
The probability of purchasing a light bulb.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Visitors of an online shop are randomly assigned to one of three groups in a between-subject design. A banner on the website invites subjects to participate in a short survey. Within the survey, subjects receive one of three information screens about the electricity savings of LED light bulbs. The survey then elicits subjects' savings beliefs. After completion of the survey, every participant receives a voucher for light bulbs.

Experimental Design Details
The experiment will be implemented in the online shop of a German appliance retailer. Potential customers who visit the website of the appliance retailer are randomly assigned to one of 3 groups. In every group, a banner is displayed on the website inviting the subject to participate in a 3-question online survey. Participation is incentivized through a 15% discount on all light bulbs of the online shop. Depending on the experimental group, survey participants receive one of the 3 screens that correspond to the treatment screens we used in the pre-registered experiment with the ID "AEARCTR-0002814":

Group 1: Subjects in group 1 receive no information screen.

Group 2: Subjects receive an information screen on the annual electricity savings of three lighting technologies (halogen, CFL, LED) in comparison to a traditional 40W incandescent light bulb. We visualize these savings by using a bar chart. In particular, subjects in this group are only informed about the savings of these light bulbs in percentage (e.g. a 4 LED saves 90% compared to the 40W incandescent). We do not inform subjects explicitly about how these relative savings in electricity costs translate into monetary savings.

Group 3: Subjects in this group receive almost the same banner as subject in group 2 but are also informed about the annual savings of the different lighting technologies in Euro. That is, besides receiving information on relative savings (in percent) we also tell them the absolute savings (in Euro). We explicitly tell the subject which electricity price and utilization of the light bulb we have assumed for calculating the monetary savings.

After our treatment intervention, subjects in all three groups receive the same questions (Q1-Q3):
Q1: "What do you think, how much would you save in annual electricity costs if you used a 4W LED light bulb instead of a 40W incandescent light bulb? Please report the annual savings in Euros."
Q2: "What do you think, how many cents do you pay per kilowatt hour? Please report a number in cents."
Q3: "How many hours per day do you use a light bulb on average? Please report a number in hours."

After completion of these questions, subjects receive a voucher code they can use on the website to get a 15% price discount on all light bulbs. The voucher code varies by experimental group.
Randomization Method
By computer.
Randomization Unit
The randomization unit is the HTTP-Cookie of the visitor.
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
Sample size: planned number of observations
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 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