Warm Glow, Social Image, and Parochialism: A Natural Field Experiment After the Climate Law Referendum

The intervention is a natural field experiment embedded in the environmental organization’s first fundraising campaign following the approval of a new climate law through a climate referendum. A total of approximately 3,367 individuals from the organization’s contact list, specifically potential and past donors, receive one of four versions of a donation request. The experiment follows a two by two design.

The first treatment dimension varies donation visibility. In the anonymous condition, donations are described as fully private. In the public recognition condition, donors are informed that they may choose to have their donation publicly acknowledged on the organization’s supporters page.
The second treatment dimension varies the framing of benefits. Half of the messages emphasize the local benefits of the newly approved climate law, while the other half emphasize its global climate benefits.

Randomization is conducted at the individual level and is stratified by past donation status and past engagement with the organization, ensuring balanced assignment across treatment groups. Each individual receives only one version of the fundraising message through the organization’s standard communication channels.

The intervention is designed to examine how donation visibility and local versus global benefit framing influence charitable giving after the provision of a public good.

2026-01-01

2026-02-28

Donation amount (conditional and unconditional), Donation (dichotomous decision variable), engagement (measured by number of cliccs per donation campaign), de registration request, request for donation to be made visible.

Secondary outcomes include:

Engagement with the donation request, measured by the number of clicks on links contained in the fundraising email during the campaign period.

Uptake of public recognition, measured by an indicator equal to one if an individual assigned to the public recognition condition requests that their donation be publicly acknowledged.

Deregistration from the mailing list, measured by an indicator equal to one if an individual requests removal from the organization’s contact list following receipt of the donation request.

Donation amount conditional on opting into public recognition, analyzed descriptively among donors in the public recognition condition who choose to make their donation visible.

The study is a natural field experiment conducted during an environmental organization’s first fundraising campaign following the approval of a new climate law through a climate referendum. Approximately 3,367 individuals from the organization’s contact list are randomly assigned to one of four treatment conditions in a two by two design. These conditions vary whether donations are described as fully anonymous or whether donors are given the option of having their donation publicly acknowledged, and whether the benefits of the climate law are framed as local or global. The public information contained here reflects only the high level features of the study design.

Not available

Randomization is conducted at the individual level. Each of the 3,367 individuals in the study sample is assigned to one of four treatment conditions in a two-by-two factorial design. Assignment is implemented in Stata using a reproducible random-number seed to ensure full replicability.

Randomization is stratified on two pre-treatment characteristics recorded in the organization’s administrative data:

Past donation status: whether the individual has ever made a prior donation to the organization;

Past engagement: whether the individual has previously interacted with the organization’s communications (e.g., opened or clicked prior messages, or participated in previous actions).

Stratification on these variables ensures balanced assignment across groups that differ in historical involvement with the organization.

Participants do not choose their treatment assignment, and the assignment is not visible to them at any stage. All individuals receive a fundraising message with an identical header, format, and general structure. Only selected lines in the body of the message vary according to the experimental condition. This design eliminates self-selection into treatment and supports unbiased estimation of intent-to-treat effects.

Within each stratum, individuals are assigned with equal probability to one of the four treatment cells (Anonymous–Local, Anonymous–Global, Public–Local, Public–Global). No cluster-level randomization is used.

individuals

No

3367 individuals

3367 individuals

Approximately equal numbers of individuals are assigned to each of the four treatment arms, with about 840 to 844 individuals per arm, for a total sample size of 3,367 individuals.

The study is individually randomized with no clustering. The planned sample size is 3,367 individuals allocated approximately equally across four arms in a two by two design. The primary contrast pools across the framing dimension and compares assignment to the public recognition condition versus the anonymous condition, yielding approximately half the sample per main arm. A formal minimum detectable effect size is not pre specified because it depends on the baseline level and variance of the main outcomes in this fundraising campaign, in particular the donation rate, the distribution of donation amounts, and the variance of link click behavior.