Identity Graph Monopoly in Advertising Markets

1. Introduction

An identity graph is a data infrastructure that links identifiers belonging to the same individual, household, device, browser, account, or organization across multiple environments. It may connect, for example:

• email addresses;
• mobile advertising IDs;
• cookies;
• IP addresses;
• device fingerprints;
• customer accounts;
• purchase histories;
• location signals;
• app activity;
• browsing behaviour; and
• inferred interests or attributes.

An identity graph monopoly in advertising markets arises where one undertaking obtains such extensive control over identity-resolution data that advertisers, publishers, data brokers, and competing ad-tech firms become dependent upon that undertaking for identifying, matching, measuring, targeting, or attributing users.

The competition problem is therefore broader than simply having a large advertising business. The concern is that control over identity infrastructure can become a bottleneck or essential input for competing advertising services.

Demand

Marginal revenue (MR)

Cost (MC)

Average total (ATC)

Profit

2040608010020406080Quantity (Q)Price (P), cost

MR = MC at Q = 52.9; demand sets P = 66.9, producing 1727.4 in economic profit.

Demand

Demand

Cost

Cost

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The conventional monopoly model helps illustrate the economic concern, although identity-graph markets have additional dimensions involving data accumulation, interoperability, privacy, switching costs, and vertical integration.

2. What Is an Identity Graph?

An identity graph attempts to determine that several identifiers represent the same underlying user.

For example:

Person A

→ Gmail address
→ smartphone advertising ID
→ browser cookie
→ shopping account
→ connected-TV identifier
→ loyalty-card account
→ app account
→ household IP address

may be treated as a single identity cluster.

The graph can consequently allow an advertising intermediary to answer:

"Which advertising identifiers correspond to the same potential consumer?"

This has substantial competitive value because advertising markets depend heavily upon the ability to:

1. identify audiences;
2. target advertisements;
3. measure conversions;
4. prevent duplicate exposure;
5. attribute sales;
6. construct look-alike audiences;
7. measure reach and frequency; and
8. connect online and offline activity.

3. How an Identity-Graph Monopoly Can Develop

A. Data accumulation

The first mechanism is data accumulation.

A firm operating a search engine, social network, mobile operating system, browser, advertising exchange, payment service, or e-commerce platform may obtain enormous quantities of first-party information.

The more services it controls, the more identifiers it can connect.

This creates a feedback loop:

More users → more identifiers → better identity matching → better advertising performance → more advertisers → more revenue → greater ability to acquire data

B. Cross-service identity linking

The monopolistic advantage becomes stronger when the same undertaking controls several digital services.

For example:

Search + browser + mobile OS + video + maps + advertising exchange + publisher tools

can provide numerous opportunities for identity resolution.

A rival identity provider may have only one or two sources of data.

The incumbent therefore possesses a structural advantage even if competitors can technically build identity graphs.

4. Network Effects

Identity graphs exhibit important data-driven network effects.

Suppose an identity graph initially identifies 100 million users with 80% accuracy.

An advertiser may contribute additional conversion information.

That information improves the graph.

Improved matching attracts additional advertisers and publishers.

Those participants generate further information.

The result can be:

larger graph → better matching → better advertising → greater participation → more data → larger/better graph

This can produce a self-reinforcing competitive advantage.

5. Identity Graph as an Essential Advertising Input

The central competition-law question is whether an identity graph should be regarded as merely a valuable dataset or as a critical infrastructure/input.

The argument for the latter becomes stronger where:

1. advertisers cannot effectively target users without it;
2. publishers cannot effectively monetize inventory without it;
3. rival ad-tech firms cannot obtain equivalent data;
4. duplication of the graph is economically impractical;
5. switching would cause substantial loss of historical data;
6. interoperability is technically restricted; and
7. the identity provider itself competes downstream in advertising.

In that situation, the identity graph can operate as a vertical bottleneck.

6. Vertical Integration

Identity monopolization becomes particularly problematic where the identity provider also operates downstream advertising services.

A simplified structure is:

Identity data

↓

Identity resolution

↓

Audience segmentation

↓

Ad exchange / ad-serving

↓

Advertiser

A vertically integrated company could potentially use its control over the upstream identity layer to disadvantage downstream competitors.

Possible conduct includes:

• restricting access;
• degrading interoperability;
• preferentially providing data to its own advertising products;
• imposing discriminatory access conditions;
• changing identifier standards;
• limiting third-party measurement;
• tying identity services to advertising services; and
• using privileged identity information to improve its own targeting.

7. Privacy as a Competitive Variable

Identity graphs also demonstrate why privacy cannot always be separated from competition law.

A platform may claim that restrictions on third-party identity access are necessary to protect privacy.

That justification may be legitimate.

But competition authorities may ask whether:

the same privacy restriction is applied neutrally to all market participants, or whether it disproportionately eliminates competing advertising intermediaries while preserving the platform's own advertising capabilities.

The relevant distinction is therefore:

privacy protection
versus
privacy restrictions selectively disadvantaging rivals.

This issue is especially significant where the platform continues to use its own first-party data while preventing competitors from accessing equivalent signals.

8. Identity Graph Monopoly and Data Advantage

A dominant identity graph can create several forms of competitive advantage.

8.1 Targeting advantage

The firm can identify audiences more accurately.

8.2 Measurement advantage

It can associate advertisements with subsequent consumer activity.

8.3 Attribution advantage

It can claim greater ability to demonstrate that an advertisement produced a purchase.

8.4 Frequency-management advantage

It can recognize users across multiple devices and reduce or increase advertising exposure.

8.5 Audience-building advantage

It can construct increasingly sophisticated audience segments.

8.6 Fraud-prevention advantage

It can identify suspicious or duplicate accounts more effectively.

These advantages can collectively make the identity graph difficult for competitors to replicate.

9. Relevant Market Definition

Several markets may need to be examined separately.

Possible Market 1: Identity-resolution services

The relevant service may be the provision of identity-matching infrastructure to advertising businesses.

Possible Market 2: Audience data

The relevant market may concern commercial audience-information services.

Possible Market 3: Ad verification and measurement

Identity information may constitute an important input into advertising measurement.

Possible Market 4: Ad intermediation

The identity graph may support a broader advertising-intermediation market.

Possible Market 5: Online display advertising

Identity infrastructure may ultimately support competition in display advertising.

The proper market depends upon substitutability rather than the technological label "identity graph."

10. Foreclosure Theories

A. Refusal to supply

A dominant identity provider may refuse access to identity-resolution functionality.

The competition question is whether access is sufficiently indispensable and whether the refusal eliminates effective competition downstream.

B. Discriminatory access

The undertaking may technically provide access but offer:

• superior access to itself;
• delayed access to competitors;
• less accurate identifiers to rivals;
• higher prices to independent ad-tech firms; or
• different technical standards.

This can constitute a more subtle form of foreclosure.

C. Self-preferencing

The identity provider may rank, prioritize, or otherwise advantage its own advertising products.

For example:

Identity graph → own ad exchange

may receive richer information than:

Identity graph → rival ad exchange

This can distort competition without an outright refusal to supply.

D. Data tying

Identity services may be tied to:

• advertising exchanges;
• demand-side platforms;
• publisher tools;
• analytics;
• measurement services; or
• ad-serving products.

The concern is that customers may effectively be required to purchase the dominant firm's downstream services to obtain access to identity capabilities.

11. Privacy Sandbox-Type Competition Issues

Changes from third-party cookies toward platform-controlled identity and measurement systems illustrate a particularly important problem.

Suppose a dominant browser eliminates third-party tracking.

That may improve privacy.

But if the browser simultaneously provides itself with alternative first-party or proprietary advertising signals unavailable to competitors, the competitive effect may be asymmetric.

The legal inquiry therefore becomes:

1. Is the restriction genuinely privacy-driven?
2. Is it proportionate?
3. Is it applied equally?
4. Does it advantage the platform's own advertising business?
5. Are effective alternatives available?
6. Does the change eliminate competing ad-tech capabilities?

12. Important Case Laws

The following cases are particularly useful for analysing identity-graph monopoly theories, even though many do not literally use the term "identity graph." They establish the underlying principles concerning data advantages, digital platforms, self-preferencing, tying, essential inputs, and exclusionary conduct.

1. Google Search (Shopping) — European Commission / General Court

The Google Shopping litigation is highly relevant to identity-graph theories because it demonstrates how a platform controlling an important digital infrastructure can potentially use that position to advantage its own downstream service.

The case concerned Google's treatment of comparison-shopping services and the preferential positioning of Google's own comparison-shopping service.

Relevance

The principle can be extended conceptually to identity infrastructure:

dominant upstream digital infrastructure → preferential treatment of own downstream advertising service

The case is therefore useful for analysing self-preferencing and leveraging theories involving identity data.

Competition principle

Dominance in one digital layer can potentially be used to distort competition in an adjacent layer where rivals depend upon access to the dominant platform's infrastructure.

2. Google Android — European Commission / General Court

The Google Android proceedings examined Google's conduct concerning the Android ecosystem, including contractual restrictions involving search and browser distribution.

Relevance to identity graphs

Identity infrastructure can similarly become embedded within a wider ecosystem.

A dominant mobile operating system may control:

• device identifiers;
• application distribution;
• browser access;
• authentication;
• user accounts; and
• advertising interfaces.

The Android litigation demonstrates the importance of analysing ecosystem leverage, rather than examining an individual digital service in isolation.

Competition principle

A dominant platform can potentially extend its power from one layer of a digital ecosystem into neighbouring markets.

3. Google AdSense — European Commission / General Court

The Google AdSense case is particularly relevant because it directly concerns online advertising.

The Commission examined contractual restrictions that limited the ability of third-party websites to display search advertisements from competing providers.

Relevance

An identity graph could operate as an upstream input into advertising intermediation.

If a dominant undertaking controls identity information and then imposes restrictions preventing publishers or advertisers from using competing advertising technologies, the same basic foreclosure concern arises.

Competition principle

Control over an important advertising input can be used to restrict the competitive opportunities of rival advertising intermediaries.

4. Facebook / Meta — German Federal Cartel Office

The German competition authority's proceedings concerning Facebook's combination of data from different services are among the most important precedents for understanding the relationship between data accumulation, platform dominance, and competition law.

The case concerned Facebook's ability to combine user information originating from different services and sources.

Relevance to identity graphs

This is extremely important conceptually.

An identity graph is fundamentally concerned with linking information from multiple environments to the same user.

The case therefore demonstrates how competition law may scrutinize the ability of a dominant platform to combine data across services.

Competition principle

Data-combination practices can have competition significance where a dominant platform's market power allows it to impose data-processing conditions that reinforce its position.

5. Bundeskartellamt v Facebook / Meta — German Federal Court of Justice

The German Federal Court of Justice's treatment of the Facebook matter is important because it recognized the relationship between competition-law power and data-processing conditions.

Relevance

The case illustrates that data practices cannot necessarily be treated as competitively irrelevant merely because the immediate transaction does not involve a conventional monetary price.

Identity graphs are often built through extensive collection and combination of data supplied by users.

Competition principle

The economic significance of data collection and combination can be examined in the context of market power and exploitative or exclusionary effects.

6. United States v. Google — Ad Tech

The U.S. Google ad-tech litigation is directly relevant to the architecture of digital advertising.

The U.S. Department of Justice alleged that Google had unlawfully maintained monopoly power across important parts of the digital advertising technology stack.

Relevance to identity graphs

An identity graph can sit between:

publishers → ad-tech infrastructure → advertisers

If the same company controls multiple layers, identity information can potentially reinforce vertical integration.

Competition principle

Control over interconnected advertising infrastructure can create opportunities for exclusionary conduct when a firm operates simultaneously at multiple levels.

7. FTC v. Facebook

The U.S. Federal Trade Commission's Facebook litigation concerned alleged maintenance of monopoly power in personal social networking.

Although not an identity-graph case specifically, the case is highly relevant because Facebook's competitive position has historically involved strong network effects, user data, and ecosystem advantages.

Relevance

Identity graphs can magnify these effects.

A platform that possesses extensive information about users may make it difficult for competitors to reproduce equivalent targeting and audience capabilities.

Competition principle

Network effects, switching costs, and accumulated data can contribute to durable platform market power.

8. United States v. Microsoft

The Microsoft case remains a foundational precedent for technological tying and exclusionary conduct.

Microsoft used its dominant operating-system position in ways that the courts found unlawfully restrained competition in browser markets.

Relevance to identity infrastructure

An identity provider controlling an important technological platform could similarly attempt to condition access to one layer upon use of another service.

For example:

platform identity → mandatory advertising service

could raise issues analogous to technological tying where the legal elements are otherwise satisfied.

Competition principle

A dominant technological platform cannot necessarily use control of one important layer to exclude competitors in another.

9. Bronner v Mediaprint

The European Court of Justice's decision in Oscar Bronner GmbH & Co. KG v Mediaprint is important for the essential-facilities dimension of identity infrastructure.

The Court applied a demanding test to claims requiring access to infrastructure controlled by another undertaking.

Relevance

A claimant arguing that an identity graph must be made available to competitors would need to address questions such as:

• Is access indispensable?
• Can the service realistically be duplicated?
• Is there a viable alternative?
• Would refusal eliminate effective competition?

Competition principle

Dominance alone does not automatically create an obligation to supply competitors.

10. IMS Health v NDC Health

The IMS Health litigation is particularly significant for essential-facility reasoning involving information structures and interoperability.

The dispute concerned access to a pharmaceutical data structure.

Relevance to identity graphs

An identity graph is itself a structured information system.

Where competitors cannot realistically reproduce an indispensable data architecture, the IMS Health principles become highly relevant.

Competition principle

Under stringent circumstances, refusal to license or provide access to an indispensable information infrastructure may constitute an abuse of dominance.

11. Magill

The Magill cases established an important European framework concerning refusal to provide information and exceptional circumstances in which compulsory access may be required.

Relevance

Identity graphs may contain information that competitors need for:

• advertising measurement;
• identity matching;
• attribution;
• fraud prevention; and
• audience targeting.

The case therefore provides part of the doctrinal background for assessing whether withholding information can become exclusionary.

12. Slovak Telekom

Slovak Telekom concerned exclusionary conduct involving access conditions and margin-squeeze theory in telecommunications.

Relevance

Identity infrastructure may similarly be situated between an upstream service and downstream advertising services.

If the dominant firm controls an identity input and simultaneously competes downstream, pricing or access conditions could potentially produce a margin-squeeze-type problem where the relevant legal requirements are met.

Competition principle

Vertical control over an essential or important input can create exclusionary risks when the supplier is simultaneously active downstream.

13. Overall Legal Test

An identity-graph monopoly should not automatically be regarded as unlawful merely because a firm possesses a large quantity of identity data.

Competition authorities would generally need to examine several questions.

Step 1 — Dominance

Does the undertaking possess substantial market power in:

• identity services;
• advertising technology;
• audience data;
• advertising intermediation; or
• another relevant market?

Step 2 — Control

Does the undertaking control an identity resource that rivals cannot reasonably reproduce?

Step 3 — Competitive significance

Does the resource materially affect:

• targeting;
• measurement;
• attribution;
• reach;
• fraud prevention; or
• advertising effectiveness?

Step 4 — Conduct

Has the undertaking:

• refused access;
• degraded interoperability;
• discriminated between users;
• self-preferenced;
• tied services;
• bundled products;
• restricted data portability; or
• imposed exclusionary contractual terms?

Step 5 — Effect

Does the conduct:

• exclude rivals;
• raise their costs;
• reduce innovation;
• increase barriers to entry;
• reduce advertiser choice; or
• reinforce the incumbent's position?

Step 6 — Justification

Are restrictions justified by:

• privacy;
• cybersecurity;
• fraud prevention;
• technical integrity;
• consumer protection; or
• legitimate product-design considerations?

Step 7 — Proportionality

Even where a legitimate objective exists, authorities may need to examine whether the restriction is:

necessary + proportionate + non-discriminatory.

14. Identity Graph Monopoly vs Ordinary Data Advantage

The distinction is important.

Therefore, the mere possession of data does not establish monopoly power.

The stronger theory is that identity resolution itself becomes a strategically indispensable layer of advertising infrastructure.

15. Competitive Harms

An identity-graph monopoly can produce several forms of harm.

15.1 Entry barriers

New ad-tech firms cannot obtain equivalent identity coverage.

15.2 Higher advertising costs

Advertisers may face fewer competing intermediaries.

15.3 Reduced publisher choice

Publishers may become dependent upon one identity provider.

15.4 Lower innovation

Rivals may be unable to develop alternative targeting and measurement systems.

15.5 Data feedback loops

The incumbent continuously improves its graph while competitors lose access to comparable data.

15.6 Increased surveillance concentration

One firm obtains an unusually comprehensive picture of consumer behaviour.

15.7 Reduced contestability

Even if the incumbent's prices initially remain competitive, rivals may become structurally incapable of challenging it.

16. Remedies

Competition authorities could consider several remedies.

A. Interoperability

Require technically reasonable interoperability between identity systems.

B. Data portability

Allow users or businesses to transfer relevant data where legally permissible.

C. Non-discrimination

Require equivalent access conditions for the dominant firm's advertising business and competitors.

D. Data-use separation

Prevent information obtained in one market from being selectively used to advantage another business.

E. Structural separation

In particularly serious cases, separate identity infrastructure from downstream advertising activities.

F. Transparency

Require disclosure of material changes to identity and measurement systems.

G. Independent auditing

An independent mechanism could examine whether competitors receive equivalent technical treatment.

17. Key Doctrinal Tension

The most difficult legal problem is balancing privacy and competition.

A dominant platform may legitimately argue:

"We restrict third-party identity access because unrestricted tracking harms users."

The competition authority must then distinguish between:

genuine privacy-enhancing architecture

and

privacy architecture that simultaneously preserves the incumbent's informational advantage and eliminates competitors.

This makes identity-graph cases substantially more complicated than traditional monopolization cases.

18. Conclusion

An identity graph monopoly in advertising markets arises when control over identity resolution becomes a source of durable market power rather than merely a valuable data asset.

The most important competition-law concern is the combination of:

identity data + identity resolution + network effects + vertical integration + advertising infrastructure.

The strongest theories involve a dominant undertaking using control over identity infrastructure to foreclose rival ad-tech providers, restrict interoperability, self-preference its advertising services, discriminate in data access, or exploit cross-market data advantages.

The most relevant precedents include Google Shopping, Google Android, Google AdSense, Facebook/Meta, Google Ad Tech, FTC v Facebook, Microsoft, Bronner, IMS Health, Magill, and Slovak Telekom. Together they provide the legal framework for analysing dominance, leveraging, self-preferencing, refusal to supply, essential facilities, tying, data combination, and vertical foreclosure in identity-driven advertising ecosystems.

Core proposition: the competition-law significance of an identity graph does not arise simply because it contains enormous amounts of personal data. It arises when the graph becomes a bottleneck infrastructure through which competitors must identify, reach, measure, or attribute users, particularly where its controller simultaneously competes in the downstream advertising market.