平台有最优规模吗?——基于不同收费结构的视角

Is There the Optimal Scale for Platform?——Based on the Perspective of Different Pricing Structure

交叉网络外部性的存在是网络平台规模不断扩张的原因之一。但实际经济中所观察到的情形却与理论相悖,天猫、京东等电子商务平台并未在竞争中一味扩大规模,而是不断提高店铺续签门槛,拒签销售额较低的店铺,这意味着平台在主动约束规模的扩张,原因何在?基于双边市场理论,构建理论分析模型,在双边免费、双边收费与单边收费等不同收费结构下,重点考察卖方竞争对平台规模决策的影响以及对应的社会福利变化情况。结果表明:当平台利润主要来源于卖方时,为避免卖方过度竞争导致利润受损,平台倾向于限制卖方数量,并将在某一规模上达到最优;比较平台限制卖方数量与不限制卖方数量的社会福利发现,当使用平台的买方数量越多,或拐点处平台的卖方数量越多,或卖方间竞争性越小,则平台限制卖方数量所导致的社会福利损失越大。因此,建议将电子商务平台主动约束规模从而限制卖方竞争的行为纳入监管。

The Cross-group externality is one of the reasons why the scale of platforms will continue to expand.However,in the circumstances observed in the real economy,it goes against theory.There are some e-commerce platforms,such as Tmall and JingDong,which are constantly raising the threshold of renewing contracts,and refusing to serve the sellers with low sales.It means that platforms are actively constraining their scale,but why?Based on bilateral market theory,theoretical analysis model is constructed.The influence of seller's competition on platform's scale decision and the corresponding social welfare change are mainly investigated under different charge structures,such as bilateral free,bilateral charge and unilateral charge.The result shows that the platform tends to restrict the number of sellers to avoid profit loss caused by seller's competition,when the profit of the platform mainly comes from sellers;it's found by comparing the social benefits of limiting the number of sellers with not limiting the number of sellers that the more the number of buyers using the platform is,or the more sellers of the platform at the diversity-competitiveness turning point is,or the less competitiveness of the sellers is,the greater the social welfare loss caused by the platform limiting the number of sellers will be.As a consequence,it's suggested that the platform's behavior of restricting seller's competition should be regulated.