惩罚机制下农产品质量安全投入演化博弈分析

针对农产品质量安全问题频发和消费者对优质绿色农产品有支付能力的情景，以及农产品供应链成员质量安全投入存在正外部性问题。根据农产品供应链中供应商和生产商不同行为策略的支付矩阵，构建了供应商和生产商质量安全投入的演化博弈模型，并对模型各个参数进行求解分析。最后，进行了算例分析。结果表明：农产品供应商和生产商的质量安全投入策略与双方质量安全投入的成本收益转化率密切相关，系统演化均衡随着双方质量投入成本收益转化率而不断变化。针对农产品供应链质量投入中存在"搭便车"问题，政府惩罚力度达到某一阈值才能促使供应商和生产商同时进行质量安全投入。研究结果对政府惩罚策略的制定和供应链成员质量安全投入具有一定的启示。

Evolutionary Game of Quality and Safety Investment of Agricultural Products under Punishment Mechanism

In recent years, agricultural products accidents of quality and safety occur frequently, which has caused great harm to people's health. Since the quality and safety of agricultural products depend on all members of the agricultural supply chain, for example, suppliers, producers, sales and so on. Quality and safety problem in any link may lead to the unqualified quality of agricultural products.Improving agriculture products' quality and safety requires collective action and the design the of governance structures which overcome the information and coordination problem within the supply chain. In China, the quality and safety of agricultural products are mainly ensured and controlled by suppliers and producers. Because investment of quality and safety for agricultural product has a positive external effect, participants have an incentive to hitchhike. Then, how should the government encourage participants to increase investmentof quality and safety?An evolutionary game model is built and a replicator equation is used to describe the selection and evolution path of suppliers and producers, according to payoff matrices of different behavior strategies of suppliers and producers. Furthermore, the stable equilibrium point is calculated and the evolutionarily stable strategy of suppliers and producers behavior is obtained from the Jacobin matrix. What's more, the influence of parameters of the system is analyzed. Finally, a simulation is used to compare the results under different punishment level, and some conclusions and recommendations are provided.The results show that the investment strategy of suppliers and producers is related to the ratio of cost-benefit of quality and safety input. Some evolutionarily stable equilibrium can be found when the cost-benefit ratios change. Suppliers or producers will be reluctant to increase investment of quality and safety for the agricultural product if either of them has "free rider" behavior. Only when the government's punishmentreaches a certain threshold can the suppliers and the producers increase investment for quality and safety.The results have some inspiration for the policies-making of government institution and the agricultural firm investment strategy of quality and safety.