21世纪是中国迈进工业反哺农业、城市支持农村、建设和谐社会的崭新时期，我国农业、农村现代化以及农民问题得到有效解决将迎来一个重要的战略机遇。粮食安全作为国家战略安全的重要组成部分，是建设新农村、构建和谐社会的基础，一直是政府和学术界关注的焦点问题。从目前中国粮食生产形式来看，在各项农业政策的作用下，我国从2004年起粮食生产连续11年增产，国内粮食供需矛盾得到有效缓解。但不可否认的是，目前我国粮食安全仍然存在着许多问题：粮食流通体系不健全；粮食供求呈现区域性、结构性的矛盾；粮食核心生产区内售粮难、价格低迷等“增产不增收”现象时有发生；粮食主产区与粮食主销区间利益分配不均，区域经济发展差距不断扩大；产销区原粮与成品粮差价过大，生产者剩余与消费者剩余受损等。以上诸因素共同导致粮农生产积极性不高、粮食储备成本上升、粮食主销区抗风险能力降低等，中和了连年粮食增产带来的国家粮食安全系数的提高。

粮食流通是社会商品流通的重要组成部分，也是连接粮食生产与粮食消费的重要环节。根据马克思主义政治经济学理论，流通在市场中起着将商品资本转化为货币资本的作用。农民通过生产劳动用货币资本转化的生产资本生产出增殖了的粮食，而商品粮只有进入流通环节之后其价值才能得以体现，农民也才能获得增殖部分的货币资本。消费者的需求是引导粮食生产的根本动因，但是这种动因能否为农民所获取并将其转化为实际的市场供给则取决于粮食流通效率的高低。这正符合了流通经济学中将粮食流通视为基础性产业和先导性产业的观点。粮食流通对前决定着粮食产品的商品化、市场化程度，关乎广大消费者的切身利益；对后直接影响粮食生产、农业增效以及农民增收。从目前粮食市场运行利益分配来看，粮食流通中间商已经成为整个粮食产业链中最大的利益群，而粮食生产者与消费者的利益则被挤压。因此，粮食流通已经成为当前影响粮农收入增长、制约粮食核心生产区农业与农村经济发展、国家粮食安全保护的重要因素。

改革开放之初，国家顺应粮食供需变化对粮食流通体制进行了多次改革。1979年到1984年粮食统购统销退出市场，由计划调节向计划与市场相结合过度。1985—1997年的合同订购、市场收购和价格双轨制时期，粮食统销制度解体，粮食流通逐步放开，“保量放价”政策出台。之后是1998年以来的粮食购销市场化改革时期，尤其是2004年粮食收购市场的全面放开，粮食购销市场中的重要一员——粮食经纪人的地位得到了法律认可，同时，在全国范围内推行较高水平的粮食直接补贴，粮食市场化进程迅速推进。尽管如此，我国粮食流通市场中还存在很多问题：市场体系不健全、市场信息不畅通、粮食交易成本高等。

粮食流通体制市场化改革进一步深化时期，粮食流通效率的提升应该以市场自身的力量为主，政府则主要起引导和辅助的作用，为顺畅粮食流通创造有利条件。“十二五”时期是粮食流通体制市场化改革深化的攻坚期，能否有效解决现今粮食流通市场中的诸多问题将直接关系到“十二五”时期社会物价水平的稳定和国民消费水平的高低。市场经济条件下，粮食流通中的各利益主体是市场的决策者，只有其各自的利益得到了有效保障，才能保证粮食流通的各个环节形成完整的供应链体系，并实现粮食从核心生产区向主销区的顺利流转。但是受体制和经济发展不平衡等因素的影响，我国粮食流通中各主体的利益分配不合理，极大地阻碍了粮食流通的顺畅。从目前粮食市场利益分配来看，中间商已经成为整个粮食产业链中最大的利益群，而生产者和消费者的利益则有减无增。因此，为增加粮农收入、稳定粮食生产、平抑市场粮价、保障消费者利益，急需对粮食流通市场进行有效管控、协调粮食流通市场各主体利益分配。为解决这些问题，依托国家自科基金课题《粮食安全背景下的中国粮食生产、流通与储备协调机制研究》，在湖北省社会科学基金的资助下，我们立项从流通效率视角对粮食供应链微观主体的经济行为进行了专门研究，最终形成此书。

本书首先分解了我国粮食流通市场各利益主体及其相互之间的关系，从各主体的历史演进、利益博弈、粮食政策实施等多个层面探讨当前粮食流通市场中存在的问题。其次，构建双层市场模型，分析粮食流通市场各主体利益协调方式，从理论层面探寻影响粮食流通市场效率提升的深层次原因。同时，运用调研数据从实证角度测算粮食流通企业交易效率、技术效率、规模效率、全要素生产率，分析当前粮食流通市场交易效率和经营效率的现状及变化趋势。最后，在综合理论论证与实证研究结论的基础上，设计符合我国粮食生产、流通实际的协调粮食流通市场各主体利益的政策体系。

本书的主要内容为六个部分。

第一部分着重分析我国粮食流通市场的现状。在粮食生产能力渐趋稳定、粮食流通体制市场化改革不断深化的双重推力下，我国粮食供需安全的重心逐渐由总量安全转为依靠流通的区域供需安全。依据微观经济学理论，实现粮食流通安全的根本在于协调市场主体利益关系。现阶段，我国粮食流通市场主体利益协调尚存在诸多问题：一是市场主体发育不成熟，这种不成熟不仅体现在数量方面，还体现在利益主体的经济实力上；二是粮食购销市场与粮食生产协调不力，表现为粮食主产区与主销区利益分配失衡；三是政府政策目标与国有粮食企业市场化运行存在冲突，需要构建有中国特色的粮食流通体制调控措施。

第二部分为粮食收购市场各主体利益协调的经济学分析。运用双层市场模型分别探讨粮食收购市场中粮农、私营粮商、国有粮食收购企业等各利益主体的关系，并剖析粮食最低收购价政策的综合效应。粮食收购市场中，企业收购的粮食数量与其交易效率成正比，即企业交易效率越高，其可获粮源越多。粮食收购方交易效率低下，会产生以下几种不良影响：一是生产者剩余减少；二是粮食收购者给出的收购价格下降、收购量减少，其在收购市场中的竞争力下降，在销售市场中的利润有限，获得的总利润减少；三是市场有效供给不足、消费者面对的粮食价格高，消费者剩余减少；四是社会承担的粮食收购成本上升，国家粮食安全得不到保障。因此，降低市场交易费用、提高交易效率是协调粮食收购市场各主体利益、稳定市场秩序的突破口。

理论上，执行粮食最低收购价政策能取得较好的经济效益和社会效益。执行最低收购价政策对于消费者是不利的，但其经济损失不会太大；对于国家和整个社会来说，交易效率提高，交易费用下降，农民种粮积极性得到提高，粮食安全得到保障。该政策的实际执行也得到了社会各界的认可，但是，从笔者调研和实证研究的结果来看，粮食最低收购价政策的应有绩效并未充分体现、对粮食流通企业效率提升效果并不显著。因此，有待于从政策自身之外寻求答案。

第三部分为粮食销售市场各主体利益协调的经济学分析。该部分首先以粮食销售市场中粮食所有权的流转为线索探讨市场中各利益主体间的关系，然后运用交易费用理论分别分析市场粮源充足和市场粮源不充足两种情况下阻碍粮食跨区域流通的主要因素。研究显示：①在具有买方市场性质的粮食销售市场中，向粮食主销区提供粮食的大型粮食购销企业为了支付较少的交易费用往往倾向于降低粮食交易量；②在具有卖方市场性质的粮食销售市场中，随着粮食交易量的增加，充当粮食需求方的私营粮商支付的边际交易费用不断增加，其最终将拒绝购买更多的粮食，阻碍市场交易的完成。由此可见，促进两种情况下粮食交易顺利完成的切入点都在于降低粮食购销企业的交易费用。因此，降低购销企业的交易费用、提升企业交易效率是促进粮食在产销区之间顺畅流通的关键。

第四部分对粮食流通企业的交易效率进行测算和分析。该部分采用萨缪尔森的“冰山交易费用”模型推导出仅考虑商品价格因素的交易效率计算模型，用以测算湖北省21家粮食流通企业2006年到2008年三年间的交易效率。通过比较企业间交易效率值、企业年际交易效率波动、享受政策优惠企业的交易效率变动，得出如下结论：粮食流通行业整体交易效率处于较高水平且在不断提升，但是尚处于不稳定的曲折性提升中；企业之间的交易效率差距有不断缩小的趋势，但是单个企业交易效率的提升缺少稳定性，与行业整体交易效率水平的提升不协调；政府对个别粮食购销企业的优惠政策并未对其交易效率的提升产生明显的积极作用。

第五部分对粮食流通企业的经营效率进行测算和分析。运用DEA方法测算湖北省21家粮食流通企业从2006—2009年度的技术效率、规模效率、全要素生产率值。测算结果表明：多数粮食流通企业资源要素配置不合理，且企业对要素配置的优化过程比较随意；政府针对部分企业的政策优惠措施对行业效率影响力较小；政策倾斜和优惠有助于受惠企业效率的全面提升，但是这种正面影响缺乏持续性；随着时间的推移，粮食流通行业内企业之间的差距逐年拉大，包括经济实力和技术实力；粮食流通行业内基于技术效率增加的生产是可持续的，但是规模效率却呈逐年下降的态势；企业经营的可持续性是增强的，但是这种趋势并不稳定。

第六部分为粮食流通市场政策体系设计。该部分从市场主体利益协调保护角度提出建设粮食流通机制：政府宏观调控下的粮食流通体制的市场化改革，政府不直接干预市场但是对粮食市场具有绝对影响力。粮食流通政策体系以国家行政职能为依托，由法律法规、扶持农业合作组织、培育市场主体、建立粮食补贴政策体系四部分组成。法律法规的完善是政策体系作用图的第一层，为粮食流通体制市场化改革提供法制化环境，既有了法律执行的强制性又剥离了政府在市场中的直接干预，有助于解决粮食安全保护过程中的难点问题。扶持农业合作组织、培育市场主体、建立粮食补贴政策体系是次于法律法规之后的第二层，即国家制定的法律法规直接作用于这三项政策措施，推进政策措施的实施。第二层次内部，粮食补贴政策体系对农合组织发展和市场主体培育都有直接作用。

本书综合运用微观经济学、博弈论与信息经济学、计量经济学以及供应链理论，采用定性与定量、文献研究与调研相结合的方法，研究粮食购销市场中各主体的利益协调问题，探寻实现粮食流通市场效率提升、各主体利益协调的途径。创新点主要体现在以下三个方面。（1）研究视角上的创新。国内现有研究粮食流通效率的文献多从粮食流通通道建设、物流环境建设、制度建设与完善等宏观层面入手，从供应链的微观层面——企业效率提升角度研究粮食流通环节各主体利益协调的文献极少。本研究从企业效率和微观供应链交叉的视角研究粮食流通环节各利益主体的协调及流通企业效率提升问题具有一定新意。（2）研究方法上的创新。本书将多层市场模型引入粮食流通市场，确定了符合粮食作为大宗商品及我国粮食生产和流通特性的双层市场模型，并结合微观经济学相关理论，对粮食流通市场中的国有粮食购销企业和私营粮食购销企业的交易效率的差异及其对市场效率的影响进行了分析和论证，为实证研究提供理论依据。（3）研究提出了政府给予购销企业政策优惠绩效的不同见解。国内现有研究多认为政府对粮食企业的政策优惠是有助于提升企业经营效率及交易效率的。本书根据实证研究得出的结论提出了不同见解：政府对个别粮食购销企业的政策优惠并未对企业交易效率提升产生明显的积极作用；政府的政策倾斜和优惠有助于受惠企业经营效率的全面提升，但是这种正面影响缺乏持续性。

The 21st century is a brand-new period in which China has entered a new period in which industry feeds agriculture, cities support rural areas, and build a harmonious society. As an important part of national strategic security, food security is the foundation for building a new countryside and building a harmonious society, and has always been the focus of attention of the government and academia. From the current form of China's grain production, under the role of various agricultural policies, China's grain production has increased for 11 consecutive years since 2004, and the contradiction between domestic food supply and demand has been effectively alleviated. However, it is undeniable that there are still many problems in China's food security: the food circulation system is not perfect; There are regional and structural contradictions between food supply and demand; In the core grain production areas, the phenomenon of "increasing production without increasing income" occurs from time to time, such as difficulty in selling grain and low prices; The distribution of benefits between the main grain-producing areas and the main grain-selling areas is uneven, and the gap between regional economic development is widening; The price difference between raw grain and finished grain in production and marketing areas is too large, and the surplus of producers and consumers is damaged. The above factors have jointly led to low enthusiasm for grain and agricultural production, increased grain reserve costs, and reduced anti-risk ability in major grain marketing areas, neutralizing the improvement of national food security coefficient brought about by successive years of grain production. Food circulation is an important part of social commodity circulation, and it is also an important link connecting food production and food consumption. According to Marxist theory of political economy, circulation plays the role of converting commodity capital into monetary capital in the market. The peasants produce the multiplied grain through the production capital transformed by the production capital of the money capital through production labor, and the value of commodity grain can only be reflected after it enters the circulation link, and the peasants can also obtain the monetary capital of the multiplicated part. Consumer demand is the fundamental motivator that guides food production, but whether this motive can be obtained by farmers and converted into actual market supply depends on the efficiency of food circulation. This is in line with the view of distribution economics that grain circulation is regarded as a basic industry and a leading industry. Grain circulation determines the degree of commercialization and marketization of grain products, and is related to the vital interests of consumers; It directly affects food production, agricultural efficiency and farmers' income. From the current distribution of benefits in the operation of the grain market, grain circulation middlemen have become the largest interest group in the entire food industry chain, while the interests of food producers and consumers have been squeezed. Therefore, grain circulation has become an important factor affecting the growth of grain and agricultural income, restricting the development of agriculture and rural economy in core grain production areas, and protecting national food security. At the beginning of reform and opening up, the state carried out many reforms of the grain circulation system in response to changes in food supply and demand. From 1979 to 1984, the unified purchase and marketing of grain withdrew from the market, and the transition from planning regulation to the combination of planning and market was excessive. From 1985 to 1997, during the dual-track system of contract ordering, market purchase and price, the grain unified marketing system was dissolved, grain circulation was gradually liberalized, and the policy of "ensuring quantity and releasing prices" was introduced. Subsequently, the period of market-oriented reform of grain purchase and sales since 1998, especially in 2004, when the grain purchase market was fully liberalized, the status of grain brokers, an important member of the grain purchase and sales market, was recognized by law. Nevertheless, there are still many problems in China's grain circulation market: the market system is not perfect, the market information is not smooth, and the transaction cost of grain is high. In the period of further deepening of the market-oriented reform of the grain circulation system, the improvement of grain circulation efficiency should be based on the strength of the market itself, and the government should mainly play a guiding and auxiliary role to create favorable conditions for smooth food circulation. The "Twelfth Five-Year Plan" period is a period for deepening the market-oriented reform of the grain circulation system, and whether it can effectively solve many problems in the current grain circulation market will be directly related to the stability of the social price level and the level of national consumption during the "Twelfth Five-Year Plan" period. Under the conditions of market economy, all stakeholders in grain circulation are market decision-makers, and only when their respective interests are effectively guaranteed can they ensure that all links of grain circulation form a complete supply chain system and realize the smooth flow of grain from the core production area to the main sales area. However, affected by factors such as the imbalance of system and economic development, the unreasonable distribution of interests among various subjects in China's grain circulation has greatly hindered the smooth flow of grain. From the current distribution of interests in the grain market, middlemen have become the largest interest group in the entire food industry chain, while the interests of producers and consumers have decreased. Therefore, in order to increase the income of grain farmers, stabilize grain production, stabilize market food prices, and protect the interests of consumers, it is urgent to effectively control the grain circulation market and coordinate the distribution of interests among all entities in the grain circulation market. In order to solve these problems, relying on the project of the National Self-Science Fund "Research on the Coordination Mechanism of China's Grain Production, Circulation and Reserves in the Context of Food Security", with the funding of the Hubei Provincial Social Science Foundation, we set up a project to conduct a special study on the economic behavior of micro-subjects in the food supply chain from the perspective of circulation efficiency, and finally formed this book. This book first breaks down the various stakeholders in China's grain circulation market and their relationship with each other, and discusses the problems existing in the current grain circulation market from multiple levels such as the historical evolution of each subject, interest game, and food policy implementation. Secondly, a two-tier market model is constructed, the coordination mode of interests of various entities in the grain circulation market is analyzed, and the deep-seated reasons affecting the efficiency of the grain circulation market are explored from the theoretical level. At the same time, the survey data is used to measure the transaction efficiency, technical efficiency, scale efficiency and total factor productivity of grain circulation enterprises from an empirical perspective, and the current status and change trend of the current transaction efficiency and operational efficiency of the grain circulation market are analyzed. Finally, on the basis of comprehensive theoretical demonstration and empirical research conclusions, a policy system that coordinates the interests of all subjects in the grain circulation market in line with the actual grain production and circulation in China is designed. The main content of the book is divided into six parts. The first part focuses on the current situation of China's grain circulation market. Under the dual thrust of the gradual stabilization of grain production capacity and the deepening of the market-oriented reform of the grain circulation system, the focus of China's grain supply and demand security has gradually shifted from total security to regional supply and demand security relying on circulation. According to microeconomic theory, the fundamental to achieving the security of food circulation lies in coordinating the interests of market players. At this stage, there are still many problems in the coordination of the interests of China's grain circulation market entities: first, the immature development of market entities, which is not only reflected in quantity, but also in the economic strength of interest subjects; Second, the coordination between the grain purchase and sales market and grain production is ineffective, which is manifested in the imbalance in the distribution of interests between the main grain-producing areas and the main sales areas; Third, there is a conflict between the government's policy goals and the market-oriented operation of state-owned grain enterprises, and it is necessary to build a grain circulation system with Chinese characteristics. The second part is the economic analysis of the coordination of the interests of various entities in the grain procurement market. The two-tier market model was used to explore the relationship between grain farmers, private grain merchants, state-owned grain purchasing enterprises and other stakeholders in the grain purchase market, and the comprehensive effect of the minimum grain purchase price policy was analyzed. In the grain purchase market, the amount of grain purchased by enterprises is directly proportional to their transaction efficiency, that is, the higher the transaction efficiency of enterprises, the more food sources they can obtain. The inefficiency of grain purchaser transactions will have the following adverse effects: first, the reduction of producer surplus; Second, the purchase price and purchase volume given by grain buyers decreased, their competitiveness in the acquisition market declined, their profits in the sales market were limited, and the total profit obtained decreased; Third, the effective supply of the market is insufficient, consumers face high food prices, and consumer surplus decreases; Fourth, the cost of food purchase borne by society has risen, and national food security has not been guaranteed. Therefore, reducing market transaction costs and improving transaction efficiency is a breakthrough point for coordinating the interests of all entities in the grain purchase market and stabilizing market order. In theory, the implementation of the policy of minimum grain purchase price can achieve better economic and social benefits. The implementation of the minimum purchase price policy is unfavorable to consumers, but their economic losses will not be too great; For the country and society as a whole, transaction efficiency is improved, transaction costs are reduced, farmers' enthusiasm for growing grain is improved, and food security is guaranteed. The actual implementation of this policy has also been recognized by all sectors of society, but from the results of the author's research and empirical research, the proper performance of the minimum purchase price policy for grain has not been fully reflected, and the effect on the efficiency improvement of grain circulation enterprises is not significant. Therefore, answers remain to be sought outside the policy itself. The third part is the economic analysis of the coordination of the interests of various subjects in the grain sales market. This part first takes the circulation of grain ownership in the grain sales market as a clue to explore the relationship between various stakeholders in the market, and then uses the transaction cost theory to analyze the main factors hindering the cross-regional circulation of grain under the two conditions of sufficient grain sources and insufficient market grain sources. The study shows that: (1) in the grain sales market with the nature of a buyer's market, large grain purchasing and marketing enterprises that provide grain to the main grain sales areas tend to reduce the volume of grain in order to pay less transaction costs; (2) In a grain sales market with the nature of a seller's market, as the volume of food transactions increases, the marginal transaction costs paid by private grain merchants acting as food demanders continue to increase, and they will eventually refuse to buy more food, hindering the completion of market transactions. It can be seen that the entry point to promote the smooth completion of grain transactions in both cases lies in reducing the transaction costs of grain purchasing and marketing enterprises. Therefore, reducing the transaction costs of purchasing and selling enterprises and improving the transaction efficiency of enterprises is the key to promoting the smooth circulation of grain between production and marketing areas. The fourth part is to measure and analyze the transaction efficiency of grain circulation enterprises. This part uses Samuelson's "iceberg transaction cost" model to derive a transaction efficiency calculation model that only considers commodity price factors, which is used to measure the transaction efficiency of 21 grain circulation enterprises in Hubei Province in the three years from 2006 to 2008. By comparing the transaction efficiency value between enterprises, the fluctuation of interannual transaction efficiency of enterprises, and the transaction efficiency of enterprises enjoying preferential policies, the following conclusions are drawn: the overall transaction efficiency of the grain circulation industry is at a high level and is constantly improving, but it is still in an unstable tortuous improvement. The transaction efficiency gap between enterprises has a trend of narrowing, but the improvement of transaction efficiency of individual enterprises lacks stability, which is not in harmony with the improvement of the overall transaction efficiency level of the industry. The government's preferential policies for individual grain purchasing and marketing enterprises have not had a significant positive effect on improving their transaction efficiency. The fifth part is to measure and analyze the operating efficiency of grain circulation enterprises. The DEA method was used to calculate the technical efficiency, scale efficiency and total factor productivity of 21 grain circulation enterprises in Hubei Province from 2006 to 2009. The calculation results show that the allocation of resources and elements of most grain circulation enterprises is unreasonable, and the optimization process of factor allocation by enterprises is relatively arbitrary. The government's preferential policies for some enterprises have little impact on industry efficiency; Policy preferences and preferences can help improve the overall efficiency of beneficiary enterprises, but this positive impact is not sustainable; Over time, the gap between enterprises in the grain circulation industry has widened year by year, including economic strength and technical strength; Production based on increased technological efficiency in the food circulation industry is sustainable, but the scale efficiency is declining year by year; The sustainability of business operations is enhanced, but the trend is not stable. The sixth part is the design of the grain circulation market policy system. This part proposes the construction of a grain circulation mechanism from the perspective of coordinating and protecting the interests of market entities: the market-oriented reform of the grain circulation system under the government's macro-control, the government does not directly intervene in the market but has absolute influence on the grain market. The grain circulation policy system is based on the administrative functions of the state and consists of four parts: laws and regulations, supporting agricultural cooperative organizations, cultivating market players, and establishing a food subsidy policy system. The improvement of laws and regulations is the first layer of the role map of the policy system, which provides a legal environment for the market-oriented reform of the food circulation system, which not only has the mandatory implementation of laws but also strips away the direct intervention of the government in the market, which is helpful to solve difficult problems in the process of food security protection. Supporting agricultural cooperation organizations, cultivating market players, and establishing a food subsidy policy system are the second layer after laws and regulations, that is, the laws and regulations formulated by the state directly act on these three policy measures to promote the implementation of policy measures. At the second level, the food subsidy policy system has a direct effect on the development of IFAP and the cultivation of market subjects. This book comprehensively uses microeconomics, game theory and information economics, econometrics and supply chain theory, and adopts the method of combining qualitative and quantitative, literature research and research to study the coordination of the interests of various subjects in the grain purchase and sales market, and explore ways to improve the efficiency of the grain circulation market and coordinate the interests of all subjects. The innovation points are mainly reflected in the following three aspects. (1) Innovation in research perspective. Most of the existing literature on grain circulation efficiency in China starts from the macro level of grain circulation channel construction, logistics environment construction, system construction and improvement, and there are very few literature that studies the coordination of interests of various subjects in the food circulation link from the micro level of the supply chain - enterprise efficiency improvement. From the perspective of enterprise efficiency and micro supply chain intersection, this study studies the coordination of various stakeholders in the grain circulation link and the improvement of the efficiency of circulation enterprises. (2) Innovation in research methods. This book introduces the multi-layer market model into the grain circulation market, determines the two-tier market model that conforms to the characteristics of grain as a bulk commodity and China's grain production and circulation, and combines the relevant theories of microeconomics to analyze and demonstrate the difference in transaction efficiency between state-owned grain purchasing and marketing enterprises and private grain purchasing and marketing enterprises in the grain circulation market and its impact on market efficiency, so as to provide a theoretical basis for empirical research. (3) The study puts forward different views on the preferential performance of policies given by the government to purchasing and selling enterprises. Most existing domestic studies believe that the government's preferential policies for grain enterprises are conducive to improving the operational efficiency and transaction efficiency of enterprises. Based on the conclusions of empirical research, this book puts forward different insights: the government's policy preferences for individual grain purchasing and marketing enterprises have not had a significant positive effect on the improvement of enterprise transaction efficiency; The government's policy preferences and preferences have helped to improve the overall operational efficiency of beneficiary enterprises, but this positive impact is not sustainable.（AI翻译）