Why do digital industries routinely lead to one company having a very large share of the market (at least if one defines markets narrowly)? To anyone familiar with competition policy discussions, the answer might seem obvious: network effects, scale-related economies, and other barriers to entry lead to winner-take-all dynamics in platform industries. Accordingly, it is that believed the first platform to successfully unlock a given online market enjoys a determining first-mover advantage.
This narrative has become ubiquitous in policymaking circles. Thinking of this sort notably underpins high-profile reports on competition in digital markets (here, here, and here), as well ensuing attempts to regulate digital platforms, such as the draft American Innovation and Choice Online Act and the EU’s Digital Markets Act.
But are network effects and the like the only ways to explain why these markets look like this? While there is no definitive answer, scholars routinely overlook an alternative explanation that tends to undercut the narrative that tech markets have become non-contestable.
The alternative model is simple: faced with zero prices and the almost complete absence of switching costs, users have every reason to join their preferred platform. If user preferences are relatively uniform and one platform has a meaningful quality advantage, then there is every reason to expect that most consumers will all join the same one—even though the market remains highly contestable. On the other side of the equation, because platforms face very few capacity constraints, there are few limits to a given platform’s growth. As will be explained throughout this piece, this intuition is as old as economics itself.
The Bertrand Paradox
In 1883, French mathematician Joseph Bertrand published a powerful critique of two of the most high-profile economic thinkers of his time: the late Antoine Augustin Cournot and Léon Walras (it would be another seven years before Alfred Marshall published his famous principles of economics).
Bertrand criticized several of Cournot and Walras’ widely accepted findings. This included Cournot’s conclusion that duopoly competition would lead to prices above marginal cost—or, in other words, that duopolies were imperfectly competitive.
By reformulating the problem slightly, Bertand arrived at the opposite conclusion. He argued that each firm’s incentive to undercut its rival would ultimately lead to marginal cost pricing, and one seller potentially capturing the entire market:
There is a decisive objection [to Cournot’s model]: According to his hypothesis, no [supracompetitive] equilibrium is possible. There is no limit to price decreases; whatever the joint price being charged by firms, a competitor could always undercut this price and, with few exceptions, attract all consumers. If the competitor is allowed to get away with this [i.e. the rival does not react], it will double its profits.
This result is mainly driven by the assumption that, unlike in Cournot’s model, firms can immediately respond to their rival’s chosen price/quantity. In other words, Bertrand implicitly framed the competitive process as price competition, rather than quantity competition (under price competition, firms do not face any capacity constraints and they cannot commit to producing given quantities of a good):
If Cournot’s calculations mask this result, it is because of a remarkable oversight. Referring to them as D and D’, Cournot deals with the quantities sold by each of the two competitors and treats them as independent variables. He assumes that if one were to change by the will of one of the two sellers, the other one could remain fixed. The opposite is evidently true.
This later came to be known as the “Bertrand paradox”—the notion that duopoly-market configurations can produce the same outcome as perfect competition (i.e., P=MC).
But while Bertrand’s critique was ostensibly directed at Cournot’s model of duopoly competition, his underlying point was much broader. Above all, Bertrand seemed preoccupied with the notion that expressing economic problems mathematically merely gives them a veneer of accuracy. In that sense, he was one of the first economists (at least to my knowledge) to argue that the choice of assumptions has a tremendous influence on the predictions of economic models, potentially rendering them unreliable:
On other occasions, Cournot introduces assumptions that shield his reasoning from criticism—scholars can always present problems in a way that suits their reasoning.
All of this is not to say that Bertrand’s predictions regarding duopoly competition necessarily hold in real-world settings; evidence from experimental settings is mixed. Instead, the point is epistemological. Bertrand’s reasoning was groundbreaking because he ventured that market structures are not the sole determinants of consumer outcomes. More broadly, he argued that assumptions regarding the competitive process hold significant sway over the results that a given model may produce (and, as a result, over normative judgements concerning the desirability of given market configurations).
The Theory of Contestable Markets
Bertrand is certainly not the only economist to have suggested market structures alone do not determine competitive outcomes. In the early 1980s, William Baumol (and various co-authors) went one step further. Baumol argued that, under certain conditions, even monopoly market structures could deliver perfectly competitive outcomes. This thesis thus rejected the Structure-Conduct-Performance (“SCP”) Paradigm that dominated policy discussions of the time.
Baumol’s main point was that industry structure is not the main driver of market “contestability,” which is the key determinant of consumer outcomes. In his words:
In the limit, when entry and exit are completely free, efficient incumbent monopolists and oligopolists may in fact be able to prevent entry. But they can do so only by behaving virtuously, that is, by offering to consumers the benefits which competition would otherwise bring. For every deviation from good behavior instantly makes them vulnerable to hit-and-run entry.
For instance, it is widely accepted that “perfect competition” leads to low prices because firms are price-takers; if one does not sell at marginal cost, it will be undercut by rivals. Observers often assume this is due to the number of independent firms on the market. Baumol suggests this is wrong. Instead, the result is driven by the sanction that firms face for deviating from competitive pricing.
In other words, numerous competitors are a sufficient, but not necessary condition for competitive pricing. Monopolies can produce the same outcome when there is a present threat of entry and an incumbent’s deviation from competitive pricing would be sanctioned. This is notably the case when there are extremely low barriers to entry.
Take this hypothetical example from the world of cryptocurrencies. It is largely irrelevant to a user whether there are few or many crypto exchanges on which to trade coins, nonfungible tokens (NFTs), etc. What does matter is that there is at least one exchange that meets one’s needs in terms of both price and quality of service. This could happen because there are many competing exchanges, or because a failure to meet my needs by the few (or even one) exchange that does exist would attract the entry of others to which I could readily switch—thus keeping the behavior of the existing exchanges in check.
This has far-reaching implications for antitrust policy, as Baumol was quick to point out:
This immediately offers what may be a new insight on antitrust policy. It tells us that a history of absence of entry in an industry and a high concentration index may be signs of virtue, not of vice. This will be true when entry costs in our sense are negligible.
Given what precedes, Baumol surmised that industry structure must be driven by endogenous factors—such as firms’ cost structures—rather than the intensity of competition that they face. For instance, scale economies might make monopoly (or another structure) the most efficient configuration in some industries. But so long as rivals can sanction incumbents for failing to compete, the market remains contestable. Accordingly, at least in some industries, both the most efficient and the most contestable market configuration may entail some level of concentration.
To put this last point in even more concrete terms, online platform markets may have features that make scale (and large market shares) efficient. If so, there is every reason to believe that competition could lead to more, not less, concentration.
How Contestable Are Digital Markets?
The insights of Bertrand and Baumol have important ramifications for contemporary antitrust debates surrounding digital platforms. Indeed, it is critical to ascertain whether the (relatively) concentrated market structures we see in these industries are a sign of superior efficiency (and are consistent with potentially intense competition), or whether they are merely caused by barriers to entry.
The barrier-to-entry explanation has been repeated ad nauseam in recent scholarly reports, competition decisions, and pronouncements by legislators. There is thus little need to restate that thesis here. On the other hand, the contestability argument is almost systematically ignored.
Several factors suggest that online platform markets are far more contestable than critics routinely make them out to be.
First and foremost, consumer switching costs are extremely low for most online platforms. To cite but a few examples: Changing your default search engine requires at most a couple of clicks; joining a new social network can be done by downloading an app and importing your contacts to the app; and buying from an alternative online retailer is almost entirely frictionless, thanks to intermediaries such as PayPal.
These zero or near-zero switching costs are compounded by consumers’ ability to “multi-home.” In simple terms, joining TikTok does not require users to close their Facebook account. And the same applies to other online services. As a result, there is almost no opportunity cost to join a new platform. This further reduces the already tiny cost of switching.
Decades of app development have greatly improved the quality of applications’ graphical user interfaces (GUIs), to such an extent that costs to learn how to use a new app are mostly insignificant. Nowhere is this more apparent than for social media and sharing-economy apps (it may be less true for productivity suites that enable more complex operations). For instance, remembering a couple of intuitive swipe motions is almost all that is required to use TikTok. Likewise, ridesharing and food-delivery apps merely require users to be familiar with the general features of other map-based applications. It is almost unheard of for users to complain about usability—something that would have seemed impossible in the early 21st century, when complicated interfaces still plagued most software.
A second important argument in favor of contestability is that, by and large, online platforms face only limited capacity constraints. In other words, platforms can expand output rapidly (though not necessarily costlessly).
Perhaps the clearest example of this is the sudden rise of the Zoom service in early 2020. As a result of the COVID pandemic, Zoom went from around 10 million daily active users in early 2020 to more than 300 million by late April 2020. Despite being a relatively data-intensive service, Zoom did not struggle to meet this new demand from a more than 30-fold increase in its user base. The service never had to turn down users, reduce call quality, or significantly increase its price. In short, capacity largely followed demand for its service. Online industries thus seem closer to the Bertrand model of competition, where the best platform can almost immediately serve any consumers that demand its services.
Of course, none of this should be construed to declare that online markets are perfectly contestable. The central point is, instead, that critics are too quick to assume they are not. Take the following examples.
Scholars routinely cite the putatively strong concentration of digital markets to argue that big tech firms do not face strong competition, but this is a non sequitur. As Bertrand and Baumol (and others) show, what matters is not whether digital markets are concentrated, but whether they are contestable. If a superior rival could rapidly gain user traction, this alone will discipline the behavior of incumbents.
Markets where incumbents do not face significant entry from competitors are just as consistent with vigorous competition as they are with barriers to entry. Rivals could decline to enter either because incumbents have aggressively improved their product offerings or because they are shielded by barriers to entry (as critics suppose). The former is consistent with competition, the latter with monopoly slack.
Similarly, it would be wrong to presume, as many do, that concentration in online markets is necessarily driven by network effects and other scale-related economies. As ICLE scholars have argued elsewhere (here, here and here), these forces are not nearly as decisive as critics assume (and it is debatable that they constitute barriers to entry).
Finally, and perhaps most importantly, this piece has argued that many factors could explain the relatively concentrated market structures that we see in digital industries. The absence of switching costs and capacity constraints are but two such examples. These explanations, overlooked by many observers, suggest digital markets are more contestable than is commonly perceived.
In short, critics’ failure to meaningfully grapple with these issues serves to shape the prevailing zeitgeist in tech-policy debates. Cournot and Bertrand’s intuitions about oligopoly competition may be more than a century old, but they continue to be tested empirically. It is about time those same standards were applied to tech-policy debates.