Fanghella, ValeriaValeriaFanghellaSchleich, JoachimJoachimSchleich2025-07-222025-07-222025https://publica.fraunhofer.de/handle/publica/48982710.1016/j.jeem.2025.103213We examine the causal effect of comparative feedback (information on how an individual's carbon footprint compares to others') on costly mitigation efforts, considering beliefs in one's relative carbon footprint as a source of heterogeneity. Using a nationally representative survey experiment, we calculate respondents' carbon footprints and elicit their beliefs about their relative carbon footprint via an incentivized task. A randomly selected subset of respondents then receives comparative feedback. We measure mitigation efforts using an incentivized modified dictator game. Our results show that two-thirds of the respondents are subject to optimistic bias, i.e., underestimate their relative carbon footprints. While we find no effect of comparative feedback on average, its effect varies by respondents' relative carbon footprints and the direction of the bias. Respondents for whom comparative feedback conveys a positive signal of their prosociality - because they learn that their relative carbon footprints are small, smaller than they believed, or both - reinforce their mitigation efforts. Respondents for whom comparative feedback conveys a negative signal of their prosociality reduce or do not change their mitigation efforts. These contrasting responses result in a "divergence from the mean", deviating from the "regression towards the mean" typically observed in studies of social norms and pro-environmental behavior.enBeliefsBiasCarbon footprintSocial normsComparative feedbackClimate changejournal article