天气影响产出下“公司+农户”模式的风险补偿协调契约

Risk-Reward Contract for “Company & Farmer” Mode under Weather-Related Output Uncertainty

针对不可控天气与可控的农资投入水平均会影响农产品产出的问题,建立了由一个公司和一个农户组成的两级农产品供应链随机利润模型,比较分析了集中决策下供应链系统与分散决策下农户的最优农资投入决策,提出了天气影响产出下农产品供应链的风险补偿协调策略,在农户决策农资投入水平而公司决策收购价格的情形下,依据整个农产品生产过程中的天气情况和农资投入水平来设计风险补偿契约。研究表明:在所设计的与天气指数和农资投入水平相关的风险补偿协调契约下不利天气的影响不会改变农产品供应链的协调状态,并能有效地激励农户通过提高农资投入来保障农产品的稳定供应,进而增强农产品供应链的稳健性。最后,通过数值仿真验证了所设计的风险补偿协调契约的有效性。

Agriculture is one of the industries mostly sensitive to weather variations. In recent years, adverse weathers like mild winter, drought and low temperature have posed serious effect on the farming industry of China, for which the central committee firs document in 2011 explicitly required to speed up the construction of water conservancy works to cope with adverse weathers. However, attentions paid from the micro-perspective are still insufficient as companies and farmers under contract-fanning mode are still faced with the matching problem be^veen uncertain supply and demand as well as how to improve their own profit caused by adverse weather, which is also called agricultural product supply chain coordination problem considering the impact of adverse weather. This paper studies the coordination of a two-stage agricultural product supply chain system consisting of a company and a farmer. Considering the joint impacts of uncontrollable adverse weather and controllable investment level of agricultural materials on output, a stochastic profit model for a two-stage agricultural product supply chain is established under the newsvendor model framework. Firstly, in the basic model with risk-reward excluded, optimal strategies of the company and the farmer under decentralized setting are analyzed by employing Stackelberg game. On this basis, the farmer＇s optimal investment level in centralized setting is analyzed and compared with that of decentralized setting. Secondly, in the model with risk-reward included, a coordination strategy considering weather-related output is put forward. When the company decides purchasing price and the farmer decides agricultural material investment level, the company can design specific risk reward strategy based on weather and investment level during the production process. The results show that adverse weather reduces system-wide profit under centralized setting as well as the farmer＇s optimal investment level under decentralized setting. In the same weather index, strategies under decentralized setting distort the investment level and reduce the profit of the whole supply chain. It is proved that the supply chain can be coordinated through introducing reasonable purchasing price and the risk-reward contract both related to weather index and investment level. Besides, the designed risk reward contract has relatively little sharing economic information （once weather occurs, it becomes observable common knowledge for the company and the farmer）, and thus the risk reward contract do not restrain the behaviors of both the company and the farmer. To sum up, supply chain members can formulate the strategies according to consequences resulting from the uncontrollable adverse weather to reduce impacts of adverse weather. The designed risk reward contract can help maintain coordination and incentive the farmer to increase the agricultural input, which will guarantee steady supply and strengthen the robustness of the agricultural product supply chain.