The effect of uncertainty about future CO2-prices on green investments of retail investors

Last registered on January 31, 2024


Trial Information

General Information

The effect of uncertainty about future CO2-prices on green investments of retail investors
Initial registration date
January 29, 2024

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
January 31, 2024, 12:15 PM EST

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



Primary Investigator

University of Mannheim

Other Primary Investigator(s)

PI Affiliation
University of Mannheim/ZEW
PI Affiliation
U. Bochum
PI Affiliation
ZEW / U. Mannheim

Additional Trial Information

In development
Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
We study the effect of uncertainty about future CO2-prices on the green investment behavior of retail investors.
External Link(s)

Registration Citation

Bucher-Koenen, Tabea et al. 2024. "The effect of uncertainty about future CO2-prices on green investments of retail investors." AEA RCT Registry. January 31.
Experimental Details



Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Survey question in which participants decide if they wish to invest a hypothetical amount of 10,000 EUR either into a conventional fund or a fund that is certified to be sustainable.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
We may also study the effect of uncertainty on the perceived risk and returns of green investments.
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Particpants fill out a survey relating to CO2-prices.
Experimental Design Details
See above field "Intervention (Private)"
Randomization Method
By computer.

Specifically: We create 5 random numbers before the treatment in the survey. Participants are not able to see these random numbers, because it is hidden. Participants receiving the number 1 and 2 are the high uncertainty group. Number 3 and 4 -> Low uncertainty group. Number 5 -> control group. Basically, we have then 40% for the high uncertainty group and 40% for the low uncertainty group. 20% for control group.
Randomization Unit
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
40% of participants in group "low uncertainty", 40% of participants in group "high uncertainty", 20% of participants in control group.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
We base the power analysis on a previous survey on CO2-price uncertainty that we embedded in the German Internet Panel (GIP). The outcome variable there was an absolute EUR amount, rather than a dummy variable that we have here in the present experiment. The power analysis reveals that we need 1366 observations, spread over the two groups "high uncertainty" and "low uncertainty", to detect a 10% effect size for high uncertainty relative to low uncertainty. Specifications of the power analysis: Power (1-ß): 0,80; Type I error rate: 0,05; Equally Sized Groups; One-sided test

Institutional Review Boards (IRBs)

IRB Name
German Association for Experimental Economic Research e.V.
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