Learning about German farmers' willingness to cooperate from public goods games and expert predictions

There is a growing interest in collective contracts to address agri-environmental policy goals at landscape scales. Yet, little is known about farmers' general willingness to cooperate. We developed four treatments of a linear public goods game to investigate farmers' willingness to cooperate: (1) heterogeneous endowments, (2) leading-by-example, (3) social norms, and (4) pinpointing the socially optimal solution. Based on a sample of 358 German farmers, we find that contributions reach more than two-thirds of the initial endowment across different treatments on average. Nudging the socially optimal solution is the most effective treatment. In addition to the experiment, we elicited incentivized predictions on experimental outcomes from 212 experts. Expert beliefs on treatment effects appear to be calibrated on laboratory studies, highlighting the need to conduct, communicate, and discuss experimental studies outside the laboratory. Young female academics with an Economics background most accurately predict farmers' behaviour in the experiment.