Abstract: The definition of relevant markets is one of the core links in competitive analysis, as well as the field with the strongest technicality in anti-monopoly law. In the digital age, due to the huge indirect network effect of multilateral platforms, one side of the platforms often provides “zero-price” services. Thus, the market definition of multilateral platforms is much more complex than that of unilateral markets in the traditional economy. Considering that one side of multilateral platforms often provides services at “zero price,” non-price parameters need to be emphasized when defining the relevant market. In practice, SSNIP testing therefore needs to be adapted into SSNDQ. In the digital age, multilateral platforms may be simply classified into transactional and non-transactional ones, even though both sides of some transactional platforms, such as e-commerce platforms, can be included within the same product market. However, the Amex case in the US shows that mechanically placing both sides of a transactional platform within the same relevant market cannot fully reflect the different demand substitutions of user groups on both sides of the platform or adapt to the complex market environment in reality. How to define the relevant market of digital ecosystems has also become a concern of the competition law community. Given that the digital ecosystem mainly considers the mutual complementation among enterprises and among various products and services within an ecosystem, this essentially weakens the necessity and practicality of defining the relevant market. So far, there has been no case of defining the relevant market of the digital ecosystem globally. 

Key Words: Digital Age; Multilateral Platforms; Market Definition; Services at “Zero Price”; Digital Ecosystem

Author: Wang Xiaoye, research fellow, CASS Institute of Law;

Source: 4 (2025) Peking University Law Journal.