Can Third-Party Sellers Benefit from a Platform’s Entry to the Market?

Because of the informational advantage of online marketplaces (i.e., platforms), it is a common belief that a platform’s market entry will be detrimental to third-party sellers who sell similar products on the platform. To examine the validity of this belief, we conduct an exploratory analysis using the sales data for a single product category provided by JD.com for the month of March 2018. Our analysis reveals an unexpected result. Upon the platform’s entry, third-party sellers who sell similar products can afford to charge a higher price, obtain a higher demand, and earn a higher profit. To provide a plausible explanation for this unexpected exploratory result, we develop a duopoly model that incorporates the changing competitive dynamic before and after the platform’s entry. Specifically, before entry, the platform earns a commission (based on the seller’s revenue), whereas the seller sets its retail price as a monopoly. After entry, the platform earns a profit generated by its direct sales in addition to the commission from the seller. In addition, the seller and the platform operate in a duopoly and engage in a sequential game. By examining the equilibrium outcomes associated with this sequential game, we identify conditions under which the platform’s entry can create a win-win situation for both parties. Specifically, these conditions hold when the platform’s market potential is moderate and when the platform’s entry creates a sufficiently high spillover effect on the seller, providing a plausible explanation for our empirical finding that the seller can benefit from a platform’s entry. Funding: W. Wang acknowledges the financial support from the National Natural Science Foundation of China [Grant 72173019], the Beijing Social Science Foundation [Grant 20JJA004], the Chinese Ministry of Education Research Funds on Humanities and Social Sciences [Grant 21YJA790056], and the Excellent Young Scholar Funds of UIBE [Grant 19YQ17].