International audienceThis paper proposes an optional target-based mechanism to improve the management of groundwater withdrawals when farmers’ behavior is imperfectly monitored. It combines a classical ambient tax (a blind truncheon), paid by the group of farmers when the water table level falls below a pre-defined target, with an optional individual contract that enables signatory farmers to signal their withdrawals and to avoid the collective sanction if they comply with an individual quota (a one-eyed stick). This mechanism is expected to be more acceptable than the ambient tax and to help reduce information asymmetries between the regulator and farmers. It is tested experimentally in the lab with a contextualized protocol. First results show that such mechanism reduces withdrawals but that subjects are able to coordinate in a repeated setting to extract an informational rent
