本文建立了一个卖家和买家具有偏好异质性的双寡头数字平台的竞争模型.研究了卖家和买家均可以选择多归属(即加入两家平台)的情况下,平台基于卖家是否选择多归属对其进行三级价格歧视对社会福利以及平台定价策略的影响.研究发现该三级价格歧视会导致卖家剩余增加,但是买家剩余和社会总福利都会降低.主要原因在于价格歧视使双寡头平台对卖家的竞争更激烈,从而降低了平台针对卖家的定价.这种三级价格歧视还会改变平台针对卖家、买家的定价策略,导致倾斜定价现象出现:两家平台针对卖家的定价均降低、针对买家的定价均增加的同时还会使加入两家平台的卖家和买家数量均减少.当卖家和买家非对称或平台提供服务在任意异质性水平时,上述结论具有稳健性.
The digital economy has become an increasingly pivotal sector in the growth trajectory of China's overall economy.Digital platforms serve as the principal arenas for transactions within this digital economy,effectively acting as its backbone.While the implementation of stringent antitrust regulations has increasingly limited the capacity of these platforms to openly enforce exclusivity contracts,digital platforms still retain the ability to subtly influence users through the traditional economic tactic of discriminatory pricing.This approach is more covert.This paper aims to investigate the impact of price discrimination by digital platforms,particularly targeting sellers based on their affiliations,as a more covert means of influencing user behavior. This paper develops a competitive model for duopolistic digital platforms where both sellers and buyers exhibit heterogeneous preferences.We explore the impact on social welfare and platform pricing strategies when sellers and buyers can opt for multi-homing—that is,joining multiple platforms.Specifically,the model investi-gates the effects of third-degree price discrimination by the platforms based on whether sellers choose to multi-home or not.To capture the preferences of sellers and buyers,we employ the Hotelling model and position the duopolistic platforms at the two trisection points on the Hotelling line.This approach allows us to mitigate the interference caused by varying preferences when investigating the impact of price discrimination. The findings indicate that third-degree price discrimination leads to an increase in seller surplus while simul-taneously reducing buyer surplus and overall social welfare.The primary reason for this outcome is that price discrimination intensifies competition between the duopolistic platforms for sellers,thereby driving down the prices set for them.From the perspective of sellers,the duopolistic platforms find themselves in a Prisoner's Dilemma,intensifying competitive pressures.These escalated competitive forces subsequently cascade to the buyers,ultimately burdening buyers who are not subject to price discrimination.Specifically,the platforms raise Prices targeted at these buyers,resulting in a reduction in buyer surplus.The third-degree price discrimination also alters the platforms'pricing strategies for both sellers and buyers,giving rise to skewed pricing phenomena:both platforms lower prices for sellers and raise prices for buyers,while simultaneously reducing the number of sellers and buyers that join both platforms.An increase in the number of sellers(or buyers)joining a platform leads to enhanced positive externalities for buyers(or sellers),thereby improving overall social welfare.Howev-er,the price reductions induced by platform price discrimination fail to increase the number of sellers joining the platforms.Instead,they elevate the costs of multi-homing for sellers,leading to a reduction in their numbers and a consequent detrimental impact on social welfare.These conclusions hold stable under the conditions of asymmetry between sellers and buyers,as well as varying levels of service heterogeneity provided by the platforms. In future research,we will examine the impact of third-degree price discrimination by platforms based on whether sellers are multi-homing,specifically focusing on its impact on platform profitability.We intend to analyze this impact using methods that do not rely on explicit solutions.Furthermore,we aim to distill economi-cally meaningful and more concise conditions to ensure the existence and uniqueness of symmetric equilibria.Additionally,we will explore the effects of price discrimination on user surplus and social welfare under alterna-tive distributions of user preferences.