【作者】 高建刚；

【导师】 臧旭恒；

【作者基本信息】 山东大学 ， 产业经济学， 2007， 博士

【摘要】 以往探讨双占厂商的质量——价格竞争文献，对于质量提升成本的假设纷杂不一，且多将消费者收入(偏好)分配假定为均匀分布，在利润最大化假设下，绝大多数文献认为，两家厂商必会最大(小)化彼此的产品差异或者两家厂商的产品质量为一定的比例关系，即“最大(小)差异化原则”或者“比例差异化原则”，且一般认为生产高质量产品的厂商获得较高的利润，即所谓的“高质量优势”。而本文以消费者收入呈beta分布的分配型态，并结合成本的不同设定型态，探讨高质量优势是否成立、垂直产品差异是否符合上述原则以及不同的成本型态和收入分配型态对市场结构和社会福利的影响。此外，在上述探讨的基础上，本文还进一步就一些具体情形进行分析，如探讨社会计划者、最小质量标准、博弈顺序、网络外部性、贸易与研发政策等的存在对厂商决策、市场结构等产生的影响。本文发现，在利润最大化假设下，两家厂商会选择有质量差异的产品进行生产，即最小差异化原则不成立。厂商的质量改进成本、消费者的收入分配均对厂商决策和市场均衡有重要影响：若厂商提升产品质量不存在成本，不论消费者收入分配如何，市场均衡时，两家厂商会最大差异化各自的产品，且高质量厂商获得较高的利润，即高质量优势成立；收入分配左偏程度越大，即高收入消费者比例者越大，赫芬达尔(H)指数越大，市场集中度越高。若厂商提升产品质量的成本为固定成本，则两家厂商的产品差异不会最大化，且研发成本(系数)越大，两者的产品质量差异越小；在收入分配为左偏或者均匀分配时，高质量优势成立；当收入分配为右偏态分布时，会出现低质量厂商获得较高利润的情形，即“低质量优势”。且低质量优势的出现，并不需要低质量厂商占有较高的市场份额。若厂商提升产品质量的成本为变动成本，则两厂商会最大化彼此的产品差异；市场份额大者利润较大，反之，越小。在线性变动成本假定下，如果成本系数较大，会导致其中一家厂商的市场份额过小而退出市场。成本系数过大或者过小均会使产业的市场集中度提高。如果质量提升成本为固定成本型态：(1)、若假定市场不完全覆盖，则当中等收入水平的消费者较多时，市场上只能存在一家厂商，收入分配的集中会引起市场结构发生重要变化；(2)、最小质量标准的存在，一般会使厂商利润下降，消费者剩余提高，结果整体社会福利下降，最小质量标准越高，上述效应越明显；(3)、在动态博弈中，为了维持先动者(first-mover)优势，先进入市场者不一定选择高质量策略。先动厂商是否选择高质量策略须视消费者收入分布型态而定。在创新—模仿博弈中，如果模仿厂商具有较大的成本优势，通常创新厂商会选择低质量策略，模仿厂商会选择高质量策略，并存在后发优势；(4)、存在网络效应时，网络效应越强，高质量厂商的市场份额越大，虽然两家厂商的利润均下降，但是高质量厂商与低质量厂商的利润之比越来越大，高质量优势越明显。表明网络效应具有自强化机制——市场份额越大者，消费者效用越大，而消费者所获效用越大，厂商的市场份额越大；如果同时假定市场不完全覆盖，网络效应还会使市场均衡时只能存在一家获得正利润的厂商；(5)、在国际贸易中，一国收入分配的变化会引致其最优进出口政策发生变化。政府研发政策可能带来产品质量逆转的现象，即原本生产低质量产品的国家转而成为高质量产品生产国。本国的研发补贴越大，质量逆转现象越可能发生。且一国的收入水平越高，政府研发政策越有效。更多还原

【Abstract】 The previous literatures on the quality-price competition of Duopoly vary greatly in the assumption for the cost of quality improvement, and most of which assume the consumer income (preference) to be evenly distributed. Under the profit maximization assumption the overwhelming majority of the literature conclude that the two firms will make the quality of their products maximum different from each other or to be a certain ratio, i.e. the principle of maximum differentiation or fixed ratio. And it is generally assumed that the firm of high-quality product will have higher profit that is so-called the high-quality advantage. This paper continues to explore whether the principle of high-quality advantage proves to be true and whether vertical product differentiation complies with the above-mentioned principles based on the beta distribution of income of consumes combined with of various forms of cost. And also this paper discusses the influence of the forms of cost and the various income distributions of consumers on the market structure and social welfare. In addition, on the basis of this study, this paper will further analyze some specific impact on social welfare, decision-making of firms, market structure, such as social programmers, minimum quality standards, the game sequence, network externalities, the trade and R&D policy etc.Our Study found that the two firms under the profit maximization assumption will choose different products in quality for production, and the principle of the minimum differentiation is not valid. The costs of quality improvement and different forms of income distribution both have a major impact on the decision-making of firms and market Equilibrium.In the absence of cost of quality improvement, regardless of how the income distribution of, the two firms will make their products to be the most different in quality and the high-quality firm will make higher profit, i.e. the principle of high quality advantage is valid. The heavier the right skewed income distribution of consumers or the bigger the ratio of high-income-consumer, the greater the Herfindahl index is and the higher the degree of market concentration is.With quality dependent fixed costs the two firms will not maximize product differentiation. The bigger the R&D cost coefficient is, the smaller the difference in quality of products. For The left skewed or uniform distribution, high-quality advantage will hold; when consumers have the right skewed distribution, the low quality firm will receive a higher return, i.e. "the low-quality advantage". Also the emergence of low-quality advantage does not require the relatively high market share for the low quality firm.If the costs of quality improvement are variable ones, then the two firms will maximize their product differentiation, the firm with relatively larger market share has a higher profit. Otherwise a lower profit. Under the assumption that the cost of quality improving is linear, if the cost coefficient is very high, then one of the two firms will withdraw from the market because of too small a market share. The too big or too small cost coefficient both raises the concentration of the industry.If the cost of quality improving assumed to be the fixed: (1)when the market is not fully covered, the consumers concentrating on the middle of the market or the ration of middle-income consumers is high, then in equilibrium only one firm can survive, accordingly the market structure will experience Significant changes;(2)if there to be minimum quality standard ,then the profits of the two firms will decrease ,consumers surplus will rise, as a result the whole social welfare will go down, the higher the minimum quality standard is ,the more obvious above-mentioned effect;(3)in dynamic game, the Incumbent firm is not necessarily choose the strategy of high quality for the maintenance of advantage of the first mover. The choice of quality-locating strategy of the leading firm hinges on the form of income distribution of the consumers. In Innovation-imitation game, if imitator has a cost disadvantage, the innovative usually chooses the low-quality strategy while the imitator high-quality one and the second-mover has a higher profit.With network effect being, the stronger it is, the bigger the high-quality firm. Though the profit of the two firms goes down, the ratio of the profit of the high-quality to the low-quality becomes bigger and the high quality advantage becomes more obvious. We show in this paper that network effect has the self-reinforcing mechanism—the bigger the market share is, the bigger the consumer surplus, vice versa;(5)in international trade, the income distribution of one country will bring about changes of policy of imports and exports. The policy of R&D will also give rise to the quality reversion, i.e. a country which at first produces the low quality product becomes one producing high quality product lastly. The more the subsidy of one country is, the more emergent the phenomenon of quality reversion become. Also, the higher income standard of one country is, the more effective its R&D policy.更多还原