2.9. Guideline 9: When a Merger Involves a Multi-Sided Platform, the Agencies Examine Competition Between Platforms, on a Platform, or to Displace a Platform

Platforms provide different products or services to two or more different groups or “sides” who may benefit from each other’s participation. Mergers involving platforms can threaten competition, even when a platform merges with a firm that is neither a direct competitor nor in a traditional vertical relationship with the platform. When evaluating a merger involving a platform, the Agencies apply Guidelines 1-6 while accounting for market realities associated with platform competition. Specifically, the Agencies consider competition between platforms, competition on a platform, and competition to displace the platform.

Multi-sided platforms generally have several attributes in common, though they can also vary in important ways. Some of these attributes include:

• Platforms have multiple sides. On each side of a platform, platform participants provide or use distinct products and services. [Endnote 45] Participants can provide or use different types of products or services on each side.

• A platform operator provides the core services that enable the platform to connect participant groups across multiple sides. The platform operator controls other participants’ access to the platform and can influence how interactions among platform participants play out.

• Each side of a platform includes platform participants. Their participation might be as simple as using the platform to find other participants, or as involved as building platform services that enable other participants to connect in new ways and allow new participants to join the platform.

• Network effects occur when platform participants contribute to the value of the platform for other participants and the operator. The value for groups of participants on one side may depend on the number of participants either on the same side (direct network effects) or on the other side(s) (indirect network effects). [Endnote 46] Network effects can create a tendency toward concentration in platform industries. Indirect network effects can be asymmetric and heterogeneous; for example, one side of the market or segment of participants may place relatively greater value on the other side(s).

• A conflict of interest can arise when a platform operator is also a platform participant. The Agencies refer to a “conflict of interest” as the divergence that can arise between the operator’s incentives to operate the platform as a forum for competition and its incentive to operate as a competitor on the platform itself. As discussed below, a conflict of interest sometimes exacerbates competitive concerns from mergers.

Consistent with the Clayton Act’s protection of competition “in any line of commerce,” the Agencies will seek to prohibit a merger that harms competition within a relevant market for any product or service offered on a platform to any group of participants—i.e., around one side of the platform (see Section 4.3). [Endnote 47]

The Agencies protect competition between platforms by preventing the acquisition or exclusion of other platform operators that may substantially lessen competition or tend to create a monopoly. This scenario can arise from various types of mergers:

1. Mergers involving two platform operators eliminate the competition between them. In a market with a platform, entry or growth by smaller competing platforms can be particularly challenging because of network effects. A common strategy for smaller platforms is to specialize, providing distinctive features. Thus, dominant platforms can lessen competition and entrench their position by systematically acquiring firms competing with one or more sides of a multi-sided platform while they are in their infancy. The Agencies seek to stop these trends in their incipiency.

2. A platform operator may acquire a platform participant, which can entrench the operator’s position by depriving rivals of participants and, in turn, depriving them of network effects. For example, acquiring a major seller on a platform may make it harder for rival platforms to recruit buyers. The long-run benefits to a platform operator of denying network effects to rival platforms create a powerful incentive to withhold or degrade those rivals’ access to platform participants that the operator acquires. The more powerful the platform operator, the greater the threat to competition presented by mergers that may weaken rival operators or increase barriers to entry and expansion.

3. Acquisitions of firms that provide services that facilitate participation on multiple platforms can deprive rivals of platform participants. Many services can facilitate such participation, such as tools that help shoppers compare prices across platforms, applications that help sellers manage listings on multiple platforms, or software that helps users switch among platforms.

4. Mergers that involve firms that provide other important inputs to platform services can enable the platform operator to deny rivals the benefits of those inputs. For example, acquiring data that helps facilitate matching, sorting, or prediction services may enable the platform to weaken rival platforms by denying them that data.

The Agencies protect competition on a platform in any markets that interact with the platform. When a merger involves a platform operator and platform participants, the Agencies carefully examine whether the merger would create conflicts of interest that would harm competition. A platform operator that is also a platform participant may have a conflict of interest whereby it has an incentive to give its own products and services an advantage over other participants competing on the platform. Platform operators must often choose between making it easy for users to access their preferred products and directing those users to products that instead provide greater benefit to the platform operator. Merging with a firm that makes a product offered on the platform may change how the platform operator balances these competing interests. For example, the platform operator may find it is more profitable to give its own product greater prominence even if that product is inferior or is offered on worse terms after the merger—and even if some participants leave the platform as a result. [Endnote 48] This can harm competition in the product market for the advantaged product, where the harm to competition may be experienced both on the platform and in other channels.

The Agencies protect competition to displace the platform or any of its services. For example, new technologies or services may create an important opportunity for firms to replace one or more services the incumbent platform operator provides, shifting some participants to partially or fully meet their needs in different ways or through different channels. Similarly, a non-platform service can lessen dependence on the platform by providing an alternative to one or more functions provided by the platform operators. When platform owners are dominant, the Agencies seek to prevent even relatively small accretions of power from inhibiting the prospects for displacing the platform or for decreasing dependency on the platform.

In addition, a platform operator that advantages its own products that compete on the platform can lessen competition between platforms and to displace the platform, as the operator may both advantage its own product or service, and also deprive rival platforms of access to it, limiting those rivals’ network effects.

[Endnote 45] For example, on 1990s operating-system platforms for personal computer (PC) software, software developers were on one side, PC manufacturers on another, and software purchasers on another.

[Endnote 46] For example, 1990s PC manufacturers, software developers, and consumers all contributed to the value of the operating system platform for one another.

[Endnote 47] In the limited scenario of a “special type of two-sided platform known as a ‘transaction’ platform,” under Section 1 of the Sherman Act, a relevant market encompassing both sides of a two-sided platform may be warranted. Ohio v. American Express Co., 138 S. Ct. 2274, 2280 (2018). This approach to Section 1 of the Sherman Act is limited to platforms with the “key feature . . . that they cannot make a sale to one side of the platform without simultaneously making a sale to the other.” Id. Because “they cannot sell transaction services to [either user group] individually . . . transaction platforms are better understood as supplying only one product—transactions.” Id. at 2286. This characteristic is not present for many types of two-sided or multi-sided platforms; in addition, many platforms offer simultaneous transactions as well as other products and services, and further they may bundle these products with access to transact on the platform or offer quantity discounts.

[Endnote 48] However, few participants will leave if, for example, the switching costs are relatively high or if the advantaged product is a small component of the overall set of services those participants access on the platform. Moreover, in the long run few participants will leave if scale economies, network effects, or entry barriers enable the advantaged product to eventually gain market power of its own, with rivals of the advantaged product exiting or becoming less attractive. After these dynamics play out, the platform operator could advantage its own products without losing as many participants, as there would be fewer alternative products available through other channels.