中文摘要：

近年来，农产品销售难现象频现。组建农民专业合作社进行统一销售被普遍认为是解决这一难题的重要选择之一，但现实中提供统一销售服务的合作社却是凤毛麟角，这与国际经验形成了极大的反差。本文通过构建一个大小户合作博弈分析框架，系统阐述了合作社统一销售服务形成的条件和机理，提出了产品溢价、产业风险影响合作社提供统—销售服务的研究假说，并用来自江苏、吉林和四川3省331村240家涉及农产品销售活动的合作社调查数据进行了实证研究。研究表明，现实中进行统—销售的合作社比例极低。小农户组织起来后，产品若能获得增值溢价会显著促进合作社进行统一销售。当合作社有能力降低产业风险时，产业风险越高，农户对合作社统一销售服务的需求越强，合作社越有可能进行统一销售。现实中提供统一销售服务的合作社比例偏低的原因在于：政策激励不恰当；农户经营规模普遍较小、实力有限；农产品质量监管体系不完善。

英文摘要：

The difficulty in marketing agricultural products has often been exposed and recognized recently. The establishment of farmer cooperatives has been regarded as an effective tool. However, few cooperatives have been witnessed to provide unified sales services, which contrasts with the international experience. This article constructs a cooperative game framework and explains the mechanism of unified sales service. It puts forward research hypothesis that product premium and industrial risk can exert influence on unified sales services provision, and makes an empirical test based on data from 240 cooperatives active in product sales in 331 villages from Jiangsu, Jilin and Sichuan provinces. The results show that the proportion of cooperatives that provide unified sales services is small. The product premium is found to help increase unified sales services. Besides, if cooperatives enable to reduce industrial risk, a higher risk means farmers would have a stronger demand for unified sales services. That would mean cooperatives are more likely to provide unified sales services. The study concludes by illustrating several reasons that may account for a smaller proportion of cooperatives that provide unified sales services, such as inappropriate policy incentives, small operation scale and limited strength, as well as an imperfect quality supervision system of agricultural products.