Short-term Interventions for Long-term Change: Spreading Stable Green Norms in Networks

Strong empirical evidence suggests that people infer prevailing pro-environmental norms based on the behavior of people they encounter and engage with. These norms seem to be adopted in response to both internal motivation and social pressure. To formalize such behavior, the economic literature has introduced theoretical models that include moral and social drivers. We complement this theoretical literature by analyzing the adoption of green behavior in presence of social networks. Leveraging insights from the network-science literature, we extend an existing model of socially contingent moral motivation to include characteristics of human social behavior that have been shown, empirically, to matter for green behavior, but which have been neglected by most theoretical models. Our network moral-motivation model leads naturally to spatial-heterogeneity in environmental norms. Consistent with non-network models, we show that temporary subsidies can lead to stable equilibria with positive adoption, even when the subsidy is discontinued. In our model, however, regulators can achieve significant savings by targeting subsidies. With our computational exercises, using small semi-realistic networks, we quantify the gains of targeting subsidies, or social interventions, towards optimal seed groups. These gains may be large compared to widespread subsidies, or random selection of seed groups, and depend on the society's structural characteristics. Hence, considering social networks may change radically the performance of initiatives aimed at promoting the adoption of green behavior.