【作者】 刘苏拉；

【导师】 倪云虎；

【作者基本信息】 浙江大学 ， 国际经济与贸易， 2003， 硕士

【摘要】 过去二十年，贸易理论发生了显著变化。传统贸易理论认为，世界贸易都是小麦模式的贸易；而新贸易理论认为，世界贸易中部分是飞机模式的贸易。即使飞机模式的贸易也受到小麦模式的贸易的影响，建立在小麦模式基础上的传统贸易理论也是绝对不完整的。要解释飞机模式的贸易，必须使用报酬递增的思想(Krugman，2001)。与此同时，全球经济正在经历一场大变革，以信息技术为基础的新经济开始受到经济学家的普遍关注。相关研究发现，网络效应是报酬递增的重要源泉(Arthur，1996)，并且广泛地存在于新经济的各类产业中(McGee，Tanya，2002)。和新贸易理论强调的报酬递增不同(注重于供给方)，网络效应认为他人选择会影响个人效用，是一种基于需求方的思想，但它并未受到新贸易理论的重视。随着软件模式的贸易在世界贸易中所占份额的加大，可以确定的是，用小麦模式和飞机模式的思想来分析软件模式的贸易及其对经济的影响是不充分的。无论从学术研究的角度，还是从对现实世界的指导意义来看，将网络效应引入到贸易理论，均具有很大的价值。 网络效应的相关问题被许多经济学家广泛地探讨。Katz & Shapiro(1985)、Gilbert(1992)、Besen(1994)等人在互补性、兼容性和标准等方面做出过开拓性贡献；Arthur(1989)、Witt(1997)等人指出用户在网络间转移需要支付转换成本，并有被锁定的可能。就网络效应导致的福利问题和政府干预Hayashi(1995)、Samuelson & Varian(2001)等在其著作中有专门的描述；Gandal & Shy(2001)分析了存在网络效应时，在一定假定下政府的标准化政策。 本文研究网络效应对开展贸易时一国福利的影响。文章发现，在网络效应可跨市场传递的条件下，即使两国之间不存在任何差异，产品的生产呈报酬不变，网络效应也足以成为贸易产生的原因，因为贸易使市场规模扩大了。当网络效应不可跨市场传递时，如果贸易产品相互兼容，网络内竞争将促使一国福利获得提高；如果贸易产品互不兼容，网络间竞争会提高一国福利，此时，在位者可以谋求制定绝对优势价格。论文分七个部分。第一部分是导言。第二部分在对网络效应相关概念的简单介绍后，借用反需求曲线这一工具，指出在网络性产品的市场上可能出现局部正反馈和多重均衡。第三部分使用符合反需求曲线局部上倾的Rohlfs效用函数，分析不存在贸易时一国国内市场上垄断厂商的利润、消费者剩余和一国福利。在此基础上，第四部分探讨了网络效应跨市场传递时，贸易对一国福利的影响。第五部分分析了网络效应不可跨市场传递时的福利问题，具体又分产品相互兼容和互不兼容两种情形。在相互兼容情形下，互相开放市场可以提高一国福利，单边开放市场则减少一国福利。在互不兼容情形下，如果效用系数相差不大，存在一个价格，使本国在位者处于绝对优势地位，此时，本国福利也可获得提高。第六部分先简要介绍中国文字处理软件市场上WpS office与MSOffice竞争的背景资料，再从消费者、企业、政府三个角度展开案例分析。最后一部分是结论。 本文的创新主要包括以下几点:一、将网络效应应用到贸易和一国福利的分析中。相关文献非常稀少。二、局部正反馈思想的提出。报酬递增导致的正反馈通常被片面地理解，Mctcalfe法则在其中可能起了误导的作用[48]。无疑，一条上升的需求曲线意味着市场将吸收所有的资源，而这将引起传统经济学均衡思想的破灭。三、采用连续的效用函数。现有文献大都将消费者分成几类，给定网络大小，同一类别所有消费者得到的效用都相同。这种思想并不令人满意，因为在这种假设下，同类消费者必须集体存在于某个网络或者集体缺席于某个网络，它将导致效用函数和反需求曲线均离散。四、区分网络效应可跨市场传递和不可跨市场传递两种情形。有关文献并没有很好地区分这两种情况，而当贸易发生时，网络效应能否跨市场传递将对结论有决定性影响。更多还原

【Abstract】 During the last twenty years, there has been remarkable renovation in the trade theory area. Traditional trade theory looks on all international trades as wheat-mode trade. While Neo-trade theorists believe that some of the trades are airplane-mode trade. Even though airplane-mode trade is affected by wheat-mode trade, the traditional trade theory founded on wheat-mode trade is not absolutely comprehensive. The thought of increasing returns is indispensable in interpreting airplane-mode trade. At the same time, world economy experiences great changes. The information communication based New Economy has attracted economists’ attention. The study bearing relation on New Economy has found that network effects exists in most of the major New Economy industries and network effects is an important source of increasing returns. Increasing returns from network effects are different from those emphasized by new theory of international trade. Network effects indicate the fact that others’ selection can affected one’s utility. The thoughts are based on demand-side of markets, while neo-trade theorists don’t pay attention to it. Along with software-mode trade becoming more and more important in international trade, it is sure that it is not enough to analyze software-mode trade and its influence on economy using only thoughts of wheat-mode trade and airplane-mode trade. Introducing network effects into trade theory not only has great value in science field, but also can be used to direct activities in real world.Problems concerning network effects have been widely discussed by many economists. Katz & Shapiro, Gilbert, Besen investigated in fields of complimentarily, compatibility and standard. Arthur and Witt pointed out that being locked-in is possible for users have to pay a premium for their transfer between networks. Hayashi, Samuelson & Varian have specially described welfare and government intervention in their literatures. Gandal & Shy analyzed policies of standardization by government under certain hypothesis when network effects are evident.This paper analyzes the influence of network effects on welfare when trade happens. We find that when network effects can be transferred between markets, even in two similar countries where the production presents constant returns, trades may happen for there is enlarged market induced by network effects. When network effects can’t be transferred between markets, no matter the two kinds of products are compatible or not, competition in network can enhance welfare. In latter case, a certain price exists to acquire absolute dominance. This paper is divided into seven sections. Section one is introduction. In section two, after presenting relative conceptions, we point out that local positive feedback and multi-equilibria in the markets of networked goods may exist. We discuss monopolist’s profits, consumers’ surplus and country’s welfare in section three. Rohlfs’ utility function is used there, and the situation when new enterprise enters into the market is discussed at the end of this section. Section four discusses the case when network effects are transferable between markets, the influence of trade on profit, surplus and welfare.’Section fivediscusses the case when network effects couldn’t transfer between markets. Under this hypothesis, we distinguish two situations, that is, the two kinds of products are compatible and incompatible. In case of compatible, opening market bilaterally can help to advance one’s welfare, but opening market unilaterally will decrease one’s welfare. If case of incompatible, if the utility coefficients are the same, there exists a price which can let the incumbent maintain its monopolization, and the welfare will be increased at the same time. Section six analyzes a case about the competition between WPS Office and MS Office in Chinese market. The last section concludes.There are several innovations in this paper. First, we introduce the notion of network effects into the field of trade and welfare. Few correlative literatures exist using thi更多还原