Abstract:

In two-sided markets， the heterogeneity on the supply side and differentiation strategies have given rise to a super seller with significant bargaining power， becoming a crucial player in platform competition. Platforms cannot interfere with the independent operation of merchants， but merchants can proactively enter into exclusive agreements with platforms. A horizontal differentiation model of two-sided platform competition is constructed， analyzing the impact of the super seller's adoption of exclusive and non-exclusive strategies on platform competition， market participation of ordinary sellers， and welfare of two-sided users. It is found that the participation of the super seller changes market equilibrium， enhances the platform's pricing power over consumers， and affects the market position of ordinary sellers. Additionally， exclusive agreements enhance platform competitiveness by expanding user base and increasing pricing power. When the super seller chooses exclusive or non-exclusive agreements， they should consider both network influence and the intensity of inter-platform competition. Furthermore， it is revealed that the presence of the super seller often reduces the total welfare of ordinary sellers， while consumers tend to prefer the super seller choosing non-exclusive agreements. The main contribution of this paper lies in elucidating the impact mechanism of the super seller and their exclusive agreements， thereby providing theoretical guidance for the super seller to formulate exclusive strategies and offering policy suggestions to antitrust policymakers.

Key words: two-sided platforms, super seller, exclusive agreements, competitive bottleneck, network effects