Market definition is a core concept of competition law around the globe, including in the European Union, the United States, and Brazil. In all three jurisdictions, antitrust authorities are grappling with the challenges of digital markets, often dealing with the very same digital players. The provision of zero-price services, the multisided nature of many digital platforms, and the implementation of entire digital ecosystems all challenge traditional approaches to market definition. But where there are common problems, there is a potential for common solutions. Through a comparative analysis of decisional practice relating to these past, present, and future challenges of digital market definition, this contribution maps the common ground already achieved while highlighting remaining gaps and possible solutions: for zero-price services—the past—it shows how a consensus has emerged on the theory and possible tools to define markets for ‘free’ services. On multisided platforms—the present—it finds that no such consensus has been reached yet, but strides are currently being made in developing an overall framework. And on digital ecosystems, it analyses how this challenge of the future requires the development of a coherent approach that can be based on cross-jurisdictional insights from the past and present.

中文翻译：

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欧盟、美国和巴西的数字市场定义：过去、现在和未来

市场定义是全球竞争法的核心概念，包括欧盟、美国和巴西。在所有三个司法管辖区，反垄断机构都在努力应对数字市场的挑战，通常与相同的数字参与者打交道。零价格服务的提供、许多数字平台的多边性质以及整个数字生态系统的实施都对传统的市场定义方法提出了挑战。但是，在存在共同问题的地方，就有可能找到共同的解决方案。通过对与数字市场定义的这些过去、现在和未来挑战相关的决策实践的比较分析，本文绘制了已经达成的共同点，同时强调了剩余的差距和可能的解决方案：对于零价格服务——过去——它显示了如何在定义“免费”服务市场的理论和可能工具上达成共识。在多边平台上——目前——它发现尚未达成这样的共识，但目前正在开发一个整体框架。在数字生态系统方面，它分析了未来的这一挑战如何要求开发一种可以基于过去和现在的跨司法管辖区洞察力的连贯方法。