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Field
Abstract
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Before
This study investigates the motivations behind charitable giving after the provision of a public good, following the approval of a new climate law through a climate referendum. An environmental NGO is launching its first fundraising appeal after this policy success, creating a setting in which the public good has already been delivered and any subsequent donations reflect pure warm-glow and social-image motivations rather than instrumental effects on policy outcomes. We implement a natural field experiment with 3,367 potential donors using a 2×2 design. The first treatment dimension varies whether donations are completely anonymous or whether donors may choose public recognition on the NGO’s social media channels, allowing us to isolate warm-glow giving from social-image concerns. The second dimension varies whether the fundraising message emphasizes the local benefits of the climate law or its global climate benefits, enabling a test of parochial preferences in climate philanthropy. Randomization is stratified by past donation behavior and past engagement with the NGO. The primary outcome is the donation decision and amount. The experiment provides causal evidence on warm glow, social image, and parochial preferences in pro-environmental giving after a public good has already been provided.
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After
This study investigates the motivations behind charitable giving after the provision of a public good, following the approval of a new climate law through a referendum. An environmental NGO is launching its first fundraising appeal after this policy success, creating a setting in which the core policy outcome has already been secured. This context allows us to examine whether post-policy donations are driven primarily by expressive warm-glow motives or by instrumental considerations about continued impact.
We implement a natural field experiment with 3,367 potential donors using a 2×2 design. The first treatment dimension varies the motivational framing of the appeal: the message either emphasizes expressive participation and the symbolic value of being part of a successful civic movement (warm-glow framing), or it highlights the instrumental role of donations in financing concrete follow-up activities and ensuring effective implementation of the law (instrumental framing). The second treatment dimension varies the spatial scope of benefits emphasized in the appeal, focusing either on local benefits for Hamburg or on global climate benefits. This allows us to test whether donors exhibit parochial preferences and whether spatial scope interacts with motivational framing.
Randomization is stratified by past donation behavior, nationality and prior engagement with the NGO. The primary outcomes are the donation decision and donation amount. The experiment provides causal evidence on expressive versus instrumental motivations and on the role of spatial scope and parrochialism in pro-environmental giving after a public good has already been provided
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Trial Start Date
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Before
December 26, 2025
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After
February 23, 2025
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Last Published
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Before
January 05, 2026 06:58 AM
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After
February 19, 2026 05:17 AM
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Field
Intervention (Public)
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Before
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.
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After
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 referendum. A total of approximately 3,367 individuals from the organization’s contact list, including both past and potential donors, receive one of four versions of a donation request. The experiment follows a two-by-two design.
The first treatment dimension varies the motivational appeal of the message. In the warm-glow condition, the appeal emphasizes expressive participation and the symbolic value of being part of a successful civic movement, highlighting the collective achievement of the referendum. In the instrumental condition, the appeal emphasizes the concrete role of donations in financing follow-up activities and ensuring effective implementation of the law, thereby stressing the tangible impact of contributions.
The second treatment dimension varies the spatial scope of benefits emphasized in the appeal. Half of the messages focus on local benefits for Hamburg, while the other half highlight global climate benefits.
Randomization is conducted at the individual level and stratified by nationality, past donation status, and prior 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 why individuals donate after the successful provision of a public good, distinguishing between warm-glow and instrumental motivations and testing for parochial preferences and sensitivity to the spatial scope of benefits through variation in local versus global emphasis.
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Intervention Start Date
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Before
January 01, 2026
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After
February 23, 2026
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Primary Outcomes (End Points)
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Before
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.
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After
Donation amount (conditional and unconditional), Donation (dichotomous decision variable),
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Field
Experimental Design (Public)
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Before
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.
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After
The study is a natural field experiment conducted during an environmental organization’s first fundraising campaign following the public announcement of the approval of a climate law through a 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 the motivational appeal of the donation request, contrasting a warm-glow appeal emphasizing expressive participation and symbolic support with an instrumental appeal emphasizing the role of donations in supporting implementation of the law, and vary whether the benefits of the climate law are described in terms of local or global impact.
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Power calculation: Minimum Detectable Effect Size for Main Outcomes
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Before
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.
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After
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 analyses estimate the main effects of motivational appeal (warm-glow versus instrumental) and spatial scope (local versus global), as well as their interaction. For the estimation of main effects, observations are pooled across the complementary treatment dimension, yielding approximately half the sample in each main comparison 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.
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Intervention (Hidden)
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Before
The study is implemented as a natural field experiment embedded in an environmental organization’s first fundraising campaign following the approval of a climate law through a referendum. The target population consists of individuals on the organization’s contact list, including both potential donors and past donors. A total of 3,367 individuals are included in the randomized sample.
The experiment follows a two by two factorial design. The first treatment dimension varies donation visibility. In the anonymous condition, donations are described as fully private. In the public recognition condition, individuals are informed that they may choose to have their donation publicly acknowledged on the organization’s supporters page. Public recognition is optional and uptake is left entirely to the donor. Assignment to the public recognition condition therefore represents an offer of visibility rather than enforced disclosure.
The second treatment dimension varies the framing of benefits associated with the recently approved climate law. In the local framing condition, the donation request emphasizes benefits of the law for the jurisdiction in which the referendum took place. In the global framing condition, the donation request emphasizes global climate benefits. Given the characteristics of climate protection, the local and global framings are constructed to describe benefits of a similar nature. In particular, both framings refer to comparable mitigation and co benefit outcomes, such as reductions in carbon emissions and associated health benefits, using closely aligned language. The key difference across conditions is the geographic reference of the beneficiaries rather than the type of benefit emphasized.
Randomization is conducted at the individual level using Stata with a fixed random seed. Assignment is stratified by two pre treatment characteristics: past donation category and past engagement with the organization. Past donation is categorized into three groups: no recorded past donation, low past donation, and high past donation, based on the distribution of recorded donation amounts among past donors. Engagement is categorized into low and high engagement based on the median of a pre treatment engagement measure. Stratification ensures balanced assignment across treatment arms along both dimensions.
Each individual receives exactly one version of the donation request through the organization’s standard communication channels. There is no self selection into treatment assignment, as the subject line and initial receipt of the message are treatment independent, allowing for intention to treat estimation. All primary analyses are conducted based on initial assignment, regardless of whether individuals opt in to public recognition.
The primary analysis focuses on the effect of being offered public recognition on donation behavior. To maximize statistical power, the main visibility effect is estimated by pooling across the local and global framing conditions. Differences between local and global framing, as well as interactions between framing and visibility, are analyzed as secondary outcomes.
In addition to average treatment effects, the study examines heterogeneous effects across pre treatment characteristics. In particular, heterogeneity analyses are conducted with respect to the variables used for stratified randomization, namely past donation category and past engagement with the organization. These analyses explore whether responses to donation visibility and benefit framing differ between individuals with and without prior donation history, as well as between low and high engagement individuals.
The study also explores heterogeneity by geographic location as recorded in the organization’s contact database. Location is not used for randomization but is employed in secondary analyses to examine whether responses to local versus global benefit framing vary with geographic proximity to the jurisdiction in which the referendum took place. These analyses are exploratory in nature and are intended to assess whether place based attachment or distance from the policy context moderates donation behavior.
All heterogeneity analyses are conducted within an intention to treat framework and are interpreted as secondary or exploratory outcomes unless otherwise specified.
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After
The study is implemented as a natural field experiment embedded in an environmental organization’s first fundraising campaign following the public announcement of the approval of a climate law through a referendum. The target population consists of individuals on the organization’s contact list, including both potential donors and past donors. A total of 3,367 individuals are included in the randomized sample.
The experiment follows a two-by-two factorial design. The first treatment dimension varies the motivational appeal of the donation request. In the warm-glow condition, the message emphasizes expressive participation and the symbolic value of contributing to a successful civic movement, highlighting the collective achievement of the referendum. In the instrumental condition, the message emphasizes the concrete role of donations in financing follow-up activities and supporting effective implementation of the newly approved law, thereby stressing the tangible impact of contributions.
The second treatment dimension varies the spatial scope of benefits associated with the recently approved climate law. In the local emphasis condition, the donation request highlights benefits for the jurisdiction in which the referendum took place. In the global emphasis condition, the message highlights global climate benefits. Given the characteristics of climate protection, the local and global versions are constructed to describe comparable mitigation and co-benefit outcomes, such as reductions in carbon emissions and associated health improvements, using closely aligned language. The primary difference across conditions is the geographic scope of beneficiaries rather than the type of benefit described.
Randomization is conducted at the individual level using Stata with a fixed random seed. Assignment is stratified by nationality, past donation category, and past engagement with the organization. Past donation is categorized into three groups: no recorded past donation, low past donation, and high past donation, based on the distribution of recorded donation amounts among past donors. Engagement is categorized into low and high engagement based on the median of a pre-treatment engagement measure. Stratification ensures balanced assignment across treatment arms along these dimensions.
Each individual receives exactly one version of the donation request through the organization’s standard communication channels. There is no self-selection into treatment assignment, as the subject line and initial receipt of the message are treatment independent. All analyses are conducted within an intention-to-treat framework based on initial assignment.
The primary analysis estimates the average effects of motivational appeal and spatial scope emphasis on donation behavior, as well as their interaction. Main effects are estimated pooling across the complementary treatment dimension to maximize statistical power. The interaction between motivational appeal and spatial scope captures whether sensitivity to the geographic diffusion of benefits differs between warm-glow and instrumental appeals.
In addition to the factorial treatment effects, the study examines heterogeneity across pre-treatment characteristics, including nationality, past donation category, and past engagement with the organization. These analyses assess whether responses to motivational appeal and spatial scope vary systematically across donor history, engagement levels, and nationality.
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Secondary Outcomes (End Points)
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Before
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.
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After
Secondary outcomes include engagement with the donation request, measured by the number of clicks on campaign-related links during the fundraising period, and 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 email. These measures allow us to assess whether motivational appeal and spatial scope emphasis affect not only donation behavior but also broader engagement and potential disengagement from the organization.
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Building on Existing Work
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Before
No
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After
Yes
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