This study characterizes the optimal regulation of risky activities when the assessment of the probability of an accident is subjective. The optimism of stakeholders forms subjective risk perceptions, which substantially affect the optimal intervention. To explore this issue, we construct a moral hazard model with a limited liability constraint, where stakeholders have heterogeneous beliefs about the probability of an accident. First, we show that the optimism of a monopolist reduces the level of the preventive effort when regulatory instruments are fixed. We then analyze the case in which the regulator can set both a fine and a product price as regulatory instruments. The optimal product price increases with the monopolist’s degree of optimism, as the loose product market regulation encourages the preventive effort of the optimistic monopolist. Consequently, under such an optimal scheme, an increase in the optimism of the monopolist may increase the level of preventive effort.

当事故概率的评估是主观的时，这项研究描述了风险活动的最佳监管。利益相关者的乐观形成主观的风险感知，从而对最优干预产生重大影响。为了探讨这个问题，我们构建了一个具有有限责任约束的道德风险模型，其中利益相关者对事故概率有不同的看法。首先，我们表明，当监管工具固定时，垄断者的乐观情绪会降低预防努力的水平。然后我们分析了监管者可以同时设置罚款和产品价格作为监管工具的情况。最优产品价格随着垄断者的乐观程度而增加，因为宽松的产品市场监管鼓励了乐观垄断者的预防努力。