Abstract: The value protection contract signed in the traditional “company+farmer” model is not conducive to motivating farmers' production enthusiasm. Currently, there are few quantitative studies on social contracts, and the practice of social contracts is in urgent need of scientifically theoretical guidance. To solve this problem, this paper considers the coordination of agricultural product supply chain of farmers' production efforts and the incentive study of “company+farmer” model. From the perspective of a price change in the market, the decision model of signing social contracts when the market price is high, is constructed, and the optimization problem of companies and farmers is solved. It puts forward the contract selection rules and farmers' incentive decision under the “company+farmer” mode, clarifies the theoretical model and mechanism of social contract practice, and demonstrates its scientific nature.
The results show that: (1)When the market is poor, signing the value preservation contract can achieve the coordination and stability of the supply chain, and also the scale and efficiency of agricultural production. By locking the profits of farmers in advance, the company can stabilize the cooperation with farmers, ensure their fixed income, help farmers reduce risks in the market they face, effectively realize risk sharing and interest coordination, and effectively use and allocate resources. However, when the market is good, the value protection contract does not motivate farmers' production efforts enough, so there is a high default rate. (2)When the market is in good condition or when the market price is expected to rise, the price of agricultural products purchased by the company will follow the market if the social contract is signed, so that farmers can share the market premium generated by a price rise in the market, which encourages farmers to make production efforts, achieves supply chain coordination, and increases the total profit of the supply chain. However, the company bears all the price risks in the market, and is prone to opportunistic behaviors, or even defaults. (3)When the market is in good condition or when the market price is expected to rise, the buyback social contract signed can improve the optimal profit of the company and farmers at the same time, and realize the Pareto improvement of the non-buyback social contract, and the total profit of the supply chain can be improved. In addition, with a rise in prices, the repurchase social contract can effectively limit the blind production expansion of farmers, avoid the company's opportunistic behavior, reduce the default rate, and truly realize the “risk sharing and benefit sharing” between companies and farmers, which is an innovative way to effectively serve the “company+farmer” model. Signing the social contract when the market is good is an optimization strategy in the “company+farmer” model. The social contract with repurchase realizes Pareto improvement over the social contract without repurchase. Recently, the agricultural market has been good, and agricultural companies in Shandong, Henan and Jiangsu have adopted this practice and achieved good results.
The research results of this paper provide theoretical basis and practical guidance for enterprises and farmers to carry out practical business and cooperation in the “company+farmer” model. However, since this paper does not consider the impact of the social contract on farmers' reward, deposit setting and other provisions in the “company+farmer” model, further research and discussion can be carried out from the aspects of farmers' reward setting, risk coordination ratio and risk fund in future studies.

Key words: production efforts, “company+farmer”, social contract, supply chain coordination

摘要： 传统的“公司+农户”模式签订的保值合同不利于激励农户的生产积极性,针对这一问题,本文归纳总结实践中不同类型的社会型契约,构建在市场价格较高时签订社会型契约的决策模型,通过求解公司和农户的最优化问题,提出“公司+农户”模式下的合同选择规则和农户激励决策,明确社会型契约实际操作的内在机理。理论模型和数值分析表明,“公司+农户”模式在市场价格处于较高位或预期市场价格将上涨时,签订社会型契约可以有效激励农户的生产努力,提高生产效率与扩大生产规模;有回购的社会型契约能进一步提高整个供应链的生产效率与利润,实现帕累托改进。此外,随着价格的上涨,有回购的社会型契约能有效地限制农户的盲目生产扩张,真正做到“风险共担、收益共享”,是一种有效服务于“公司+农户”模式的创新方式。本文为“公司+农户”模式下的企业和农户开展实际业务与合作提供理论依据。

关键词: 生产努力, “公司+农户”, 社会型契约, 供应链协调