网购市场鱼龙混杂现象的经济学解释：基于二维不对称信息的视角

网络购物市场存在商品鱼龙混杂的典型现象：高价格的商品不一定高质量，低价格的商品也不一定低质量，表现出明显的信息不对称特征。文章基于网络购物市场所存在的两个维度不对称信息的特征事实，即厂商在产品质量与产品生产成本两个方面拥有私有信息，通过构建二维不对称信息的分析框架，从市场均衡的视角首次解释了上述现象的经济机理。分析表明，由于二维不对称信息的存在，消费者和厂商决策的互动过程使得市场上产品价格与质量不再具有单调递增关系，从而网络购物市场可能出现鱼龙混杂的市场均衡，文章证明了这一均衡在合理的条件下是存在的。文章通过比较静态分析考察了市场环境的变化如何影响商品质量的价格信号显示效率以及消费者购买行为，并考察了网络购物行业商家披露信息、消费者对于商家的反馈评分机制和保证退货等手段对于消除商品鱼龙混杂现象的有效性，为进一步规范发展我国网络购物行业提供了参考。

Economic Explanation of Bad-and-good-product Coexisting Phenomenon in Online Shopping Market from a Perspective of Bidimensional Asymmetric Information

There is a typical bad-and-good-product coexisting phenomenon in online shopping market:products with high prices do not always have high quality and products with low prices do not always have low quality too,showing obvious asymmetric informa-tion.Based on the stylized fact of bidimensional asymmetric information in online shopping market,namely firms have private information in the two aspects of product quality and production costs,this paper explains the economic mechanism of the abovementioned phe-nomenon from a perspective of market equilibrium for the first time by establishing an an-alytical framework of bidimensional asymmetric information.It shows that owing to bidi-mensional asymmetric information,the interaction of consumers and firms makes prices and quality of products no longer have a monotonically increasing relationship,thereby possibly leading to market equilibrium of bad-and-good-product coexisting in online shop-ping market;and it confirms the existence of this equilibrium under reasonable conditions. By a static comparison,this paper explores the effects of changes in market environment on price signaling efficiency of product quality and consumer purchase behavior as well as the effectiveness of means such as information disclosure by online shopping firms,con-sumers’feedback scoring mechanism for businesses and guaranteed return of products on the elimination of bad-and-good-product coexisting phenomenon,thereby providing refer-ence for further normative development of network industries in China.