Elasticity Estimation in Market Definition

1. Introduction

Elasticity estimation is an important economic technique used in competition law to determine the boundaries of a relevant product market or geographic market. It examines how consumers, suppliers, or competitors respond when prices or other competitive conditions change.

The most important concept is price elasticity of demand, which measures the percentage change in quantity demanded resulting from a percentage change in price:

Ed=% change in quantity demanded% change in priceE_d=\frac{\%\text{ change in quantity demanded}}{\%\text{ change in price}}

If a small price increase causes consumers to switch substantially to another product, the products are likely to belong to the same relevant market. Conversely, if consumers continue purchasing the product despite a significant price increase, the product may constitute a narrower market.

Elasticity analysis therefore assists competition authorities and courts in answering the fundamental market-definition question:

Would a hypothetical monopolist be able to profitably impose a small but significant and non-transitory increase in price?

This is closely associated with the SSNIP test.

2. Meaning of Elasticity in Competition Law

Elasticity is essentially a measure of substitutability.

For example, assume that consumers regard Products A and B as close substitutes. If the price of A rises by 5%, many consumers switch to B. Demand for A therefore falls substantially.

This suggests:

A and B exert competitive constraints on each other;

they may belong to the same relevant product market;

a monopolist controlling A alone may be unable to sustain the price increase.

By contrast, if consumers do not switch to B after A becomes more expensive, B may impose only a weak competitive constraint.

Main forms of elasticity

Own-price elasticity of demand

Cross-price elasticity of demand

Income elasticity of demand

Supply elasticity

Residual demand elasticity

Diversion ratios and switching measures

Competition authorities generally place the greatest emphasis on own-price and cross-price responses when examining market boundaries.

3. Own-Price Elasticity of Demand

Own-price elasticity measures the response of demand for a product to a change in its own price.

Suppose:

Product A price increases by 10%;

quantity demanded decreases by 20%.

Then:

Ed=−2E_d=-2

The absolute elasticity is 2, indicating relatively elastic demand.

A highly elastic demand curve means that customers can readily switch to alternatives.

A relatively inelastic demand curve indicates that alternatives impose less competitive pressure.

Competition-law significance

If a hypothetical monopolist controlling Product A cannot profitably increase its price because customers rapidly switch away, Product A should generally not be considered a market by itself.

The relevant market may need to include the products to which customers switch.

4. Cross-Price Elasticity

Cross-price elasticity examines how demand for one product changes when the price of another product changes.

EAB=%ΔQA%ΔPBE_{AB}=\frac{\%\Delta Q_A}{\%\Delta P_B}

If the price of B rises and demand for A increases substantially, A and B are potentially substitutable.

For example:

price of rail transportation rises;

demand for intercity buses increases.

A positive cross-price elasticity may therefore indicate substitution.

However, cross-price elasticity alone cannot automatically establish a relevant market.

Other considerations include:

product characteristics;

consumer preferences;

switching costs;

geographic accessibility;

capacity constraints;

contractual arrangements;

quality differences;

regulatory restrictions.

5. Elasticity and the SSNIP Test

The SSNIP test asks whether a hypothetical monopolist controlling a candidate group of products could profitably impose a small but significant and non-transitory increase in price.

Traditionally, the hypothetical increase is often around 5–10%, although the precise figure is not legally fixed.

Suppose the candidate market consists only of Product A.

If a 5% price increase results in sufficiently large switching to Product B, the price increase may be unprofitable.

The analyst therefore expands the market:

A → A + B → A + B + C

The process continues until the hypothetical monopolist could profitably sustain the price increase.

6. Critical Elasticity

Elasticity estimation can be used to calculate the critical elasticity associated with the hypothetical monopolist test.

A simplified critical-loss framework asks:

How much quantity would have to be lost following the proposed price increase before the price increase became unprofitable?

For a simplified single-product case:

Critical Loss≈ΔPΔP+MarginCritical\ Loss \approx \frac{\Delta P}{\Delta P+Margin}

where the relevant margin is generally expressed consistently with the price-increase calculation.

The estimated actual loss is then compared with the critical loss.

If:

Actual loss > critical loss

the hypothetical price increase is likely unprofitable.

If:

Actual loss < critical loss

the price increase may be profitable.

This helps determine whether the candidate market is too narrowly defined.

7. The Cellophane Fallacy

One of the most important cautions concerning elasticity-based market definition is the Cellophane fallacy.

Where a firm is already charging a monopoly price, consumers may appear highly willing to switch to alternative products following a further price increase.

This may lead investigators to conclude that many products belong to the same market.

But the observed switching may simply reflect the fact that the firm's existing price is already above the competitive level.

Thus:

High observed elasticity at the prevailing price does not necessarily prove that products are substitutes at competitive prices.

This problem is particularly important in dominance cases.

8. Case Law

1. United States v. E. I. du Pont de Nemours & Co. — Cellophane Case

United States v. E. I. du Pont de Nemours & Co., 351 U.S. 377 (1956) is one of the foundational cases concerning elasticity and market definition.

The case concerned cellophane and allegedly competing flexible packaging materials.

The Supreme Court considered whether cellophane constituted a distinct relevant market. Evidence showed substantial customer switching in response to price changes.

The Court ultimately treated the broader group of flexible packaging materials as relevant.

Importance

The case established the fundamental warning now known as the Cellophane fallacy.

Elasticity measured at an already monopolistic price may overstate substitutability.

Principle

Market definition should preferably examine competitive constraints at competitive prices, rather than simply observing switching behaviour at an already elevated monopoly price.

9. United States v. Philadelphia National Bank

In United States v. Philadelphia National Bank, 374 U.S. 321 (1963), the Supreme Court considered the relevant market in the context of banking concentration.

The Court emphasised the importance of identifying the products and geographic area in which competitive alternatives actually constrain the merging firms.

Although the case predates modern econometric elasticity analysis, its market-definition approach is important because elasticity-based evidence ultimately serves the same purpose: identifying whether customers can reasonably turn to alternatives.

Significance

The case demonstrates that market definition is not simply a mathematical exercise. Economic evidence must be connected with the commercial realities of substitution.

10. Brown Shoe Co. v. United States

Brown Shoe Co. v. United States, 370 U.S. 294 (1962) is another foundational market-definition case.

The Supreme Court examined whether different categories of shoes constituted sufficiently distinct markets.

The Court considered:

product characteristics;

industry recognition;

practical substitutability;

price differences;

customer preferences;

specialized manufacturing facilities.

Relevance to elasticity

The case illustrates why numerical price elasticity cannot be treated as the exclusive market-definition criterion.

A product may have apparently substitutable characteristics but still constitute a distinct market because consumers, producers, or commercial practices treat it differently.

11. United States v. Continental Can Co.

In United States v. Continental Can Co., 378 U.S. 441 (1964), the Supreme Court rejected an excessively narrow approach to product-market definition.

The case concerned competition between metal and glass containers.

The Court stressed the need to examine the reasonable interchangeability of products.

Relationship with elasticity

Elasticity provides an empirical way of examining reasonable interchangeability.

If consumers substantially switch from one type of container to another following changes in relative prices, cross-price elasticity may demonstrate meaningful competitive constraint.

The case therefore supports a broader economic inquiry rather than reliance on rigid product classifications.

12. United States v. Oracle Corp.

In United States v. Oracle Corp., 331 F. Supp. 2d 1098 (N.D. Cal. 2004), market definition was extensively contested in the context of enterprise software.

The parties presented economic evidence concerning:

customer substitution;

product functionality;

switching costs;

purchasing behaviour;

customer preferences;

pricing.

The case demonstrates the practical difficulty of estimating elasticity where products are differentiated and customers face substantial switching costs.

Importance

A customer may theoretically prefer another supplier but nevertheless fail to switch because of:

training investments;

data migration;

compatibility;

implementation costs;

contractual commitments.

Thus, observed elasticity may be lower than technological substitutability would suggest.

13. FTC v. Whole Foods Market, Inc.

In FTC v. Whole Foods Market, Inc., 548 F.3d 1028 (D.C. Cir. 2008), market definition concerned the competitive relationship between supermarkets and premium or natural-food supermarkets.

The litigation illustrated the importance of determining whether differentiated retail formats constrain each other's pricing.

Elasticity significance

Customers may respond differently to price changes depending upon:

store format;

geographic convenience;

product assortment;

consumer preferences;

quality;

brand positioning.

Therefore, elasticity must be estimated for the relevant consumer segment, rather than assuming uniform demand across all consumers.

14. FTC v. Staples, Inc.

In FTC v. Staples, Inc., 970 F. Supp. 1066 (D.D.C. 1997), the court considered competition between office-supply superstores.

The FTC relied substantially upon evidence showing that prices differed depending upon the number of competing office-supply superstores in a particular geographic area.

Importance for elasticity

The evidence demonstrated that the presence of competing stores affected pricing behaviour.

This supported the conclusion that the relevant market was narrower than the entire retail market for office supplies.

The case illustrates an important empirical point:

Observed pricing responses can provide indirect evidence of competitive substitution even when direct elasticity estimates are unavailable.

15. FTC v. H.J. Heinz Co.

In FTC v. H.J. Heinz Co., 246 F.3d 708 (D.C. Cir. 2001), the court considered competition in the market for jarred baby food.

The case involved highly concentrated market conditions and a proposed merger between significant suppliers.

Elasticity relevance

The analysis demonstrates that market-definition questions may depend upon whether customers view alternative products as meaningful substitutes.

Where only a limited number of firms exert significant competitive constraints, relatively small changes in the competitive relationship can substantially affect market power.

16. United States v. Microsoft Corp.

In United States v. Microsoft Corp., 253 F.3d 34 (D.C. Cir. 2001), the court examined the market for Intel-compatible PC operating systems.

The relevant market was narrowly defined because other operating systems did not impose sufficient competitive constraints.

Elasticity significance

The case illustrates an important limitation of purely functional substitutability.

A product can perform some of the same functions as another product without imposing sufficient price competition.

Factors such as:

applications compatibility;

switching costs;

network effects;

consumer expectations;

developer incentives

may substantially reduce actual substitution.

Consequently, the relevant elasticity is the effective competitive elasticity, not merely a measure of technical substitutability.

17. European Commission and EU Competition Law

European competition law generally approaches market definition through the concepts of demand-side substitutability, supply-side substitutability and potential competition.

The modern framework is strongly associated with the SSNIP methodology, although the European Commission does not mechanically require a particular econometric elasticity estimate in every case.

Elasticity evidence may be derived from:

diversion ratios;

customer surveys;

natural experiments;

switching data;

price correlations;

internal business documents;

bidding evidence;

historical pricing;

econometric estimation.

18. United Brands v Commission

In United Brands Company v Commission, Case 27/76, the Court of Justice examined the relevant product market for bananas.

The Court considered the particular characteristics of bananas and whether they were sufficiently substitutable with other fruit.

Relevance to elasticity

The judgment demonstrates that substitution depends upon more than price alone.

Factors included:

physical characteristics;

consumer preferences;

consumption patterns;

availability of alternatives;

particular uses.

Elasticity estimates must therefore be interpreted alongside qualitative evidence.

19. Hoffmann-La Roche v Commission

In Hoffmann-La Roche & Co. AG v Commission, Case 85/76, the Court dealt with dominance and market definition involving vitamins.

The Court recognised the significance of product characteristics and substitutability in determining the competitive environment.

Elasticity significance

The case is particularly useful for understanding that products with apparently similar functions may belong to separate markets if consumers perceive meaningful differences in:

quality;

characteristics;

applications;

purchasing requirements.

Elasticity must therefore be connected to actual competitive constraints.

20. Michelin v Commission

In Michelin v Commission, Case 322/81, the relevant market involved replacement tyres.

The Court considered product differentiation, customer requirements and the competitive environment.

Relevance

The case demonstrates the importance of examining customer purchasing behaviour rather than relying solely upon physical product characteristics.

Where consumers have different purchasing requirements, aggregate elasticity estimates can conceal substantial differences between customer groups.

21. Elasticity in Differentiated Digital Markets

Elasticity estimation has become particularly important in digital markets.

Traditional price-based elasticity can be difficult to apply because many digital services have:

zero monetary prices;

advertising-funded business models;

data-based compensation;

multi-sided platforms;

network effects;

quality competition.

For example, a social-media service may be "free" to users.

A conventional SSNIP test involving a monetary price increase may therefore be inappropriate.

Authorities may instead consider a:

SSNDQ — Small but Significant and Non-transitory Decrease in Quality;

increase in advertising;

reduction in privacy;

deterioration in functionality;

increase in data collection;

reduction in interoperability.

The concept of elasticity therefore increasingly extends beyond monetary prices.

22. Elasticity and Two-Sided Platforms

For platforms, elasticity can exist on several sides simultaneously.

For example:

Users → Platform

and

Advertisers → Platform

may exhibit different elasticities.

A platform could have:

low user-side price elasticity;

high advertiser-side elasticity;

strong indirect network effects.

This creates complex market-definition problems.

A price increase on one side may affect participation on another side.

Therefore, authorities must examine:

direct substitution;

cross-side network effects;

multi-homing;

switching costs;

data advantages;

platform-specific demand elasticity.

23. Elasticity and Geographic Market Definition

Elasticity is also relevant to geographic market definition.

Suppose a firm raises prices in City A.

If customers rapidly purchase from suppliers in City B, the two locations may belong to the same geographic market.

If customers do not switch because transportation costs, delivery times, regulations, or local preferences prevent substitution, the geographic market may be narrower.

Important variables include:

transport costs;

delivery costs;

travel time;

local regulations;

customer location;

supplier location;

capacity;

cross-border restrictions.

24. Supply Elasticity

Market definition cannot always be based exclusively on demand.

Supply elasticity examines how readily producers can shift production toward a product following a price increase.

Suppose a manufacturer producing Product B can rapidly and cheaply begin producing Product A.

Product B's producers may impose an immediate competitive constraint on Product A.

However, supply-side substitution is generally relevant only where suppliers can switch:

quickly;

without substantial additional investment;

without significant risk;

without abandoning their existing production arrangements.

25. Elasticity and Capacity Constraints

Elasticity estimates may be misleading when substitute suppliers lack sufficient capacity.

Suppose Product A's price increases by 10%.

Consumers theoretically want to move to Product B, but B's producers have no spare capacity.

The observed quantity switching may therefore be small even though B is a strong potential competitive constraint.

This creates an important distinction between:

Observed switching and economically feasible switching.

Competition authorities should therefore examine capacity as part of elasticity analysis.

26. Elasticity and Switching Costs

Switching costs reduce observed elasticity.

They may include:

contractual termination fees;

technical integration costs;

retraining costs;

data migration costs;

loss of accumulated data;

compatibility costs;

reputational risks;

regulatory approvals.

In digital ecosystems, switching costs can be especially important.

A consumer may regard two platforms as functionally similar but still remain with the incumbent because the cost of switching is high.

Thus:

Effective Elasticity≠Pure Functional SubstitutabilityEffective\ Elasticity \neq Pure\ Functional\ Substitutability

27. Elasticity and Network Effects

Network effects can produce asymmetric elasticity.

If most users already belong to Platform A, switching to Platform B may be unattractive because the value of B depends on having other users.

Consequently:

A price increase may not cause substantial switching;

demand may appear inelastic;

network effects may strengthen market power.

This is particularly significant in:

social networks;

payment systems;

app stores;

operating systems;

marketplaces;

communication platforms.

28. Econometric Methods for Estimating Elasticity

Competition authorities may use several empirical techniques.

A. Regression analysis

Price and quantity data can be analysed to estimate demand responses.

B. Natural experiments

A temporary price change or supply disruption may reveal actual substitution behaviour.

C. Consumer surveys

Customers may be asked what they would purchase following a hypothetical price increase.

D. Diversion ratios

Authorities can examine where customers go after abandoning a product.

E. Critical-loss analysis

Actual predicted demand loss can be compared with the loss required to make a price increase unprofitable.

F. Event studies

Historical mergers, entry, exit, or price changes may reveal competitive relationships.

29. Limitations of Elasticity Estimation

Elasticity is powerful but not conclusive.

1. Data limitations

Reliable transaction-level data may not exist.

2. Endogeneity

Prices may themselves respond to demand conditions.

3. Non-linear demand

Elasticity may vary substantially at different price levels.

4. Product differentiation

Consumers may value products differently.

5. Dynamic competition

Future entry may alter current elasticity.

6. Network effects

Demand may depend upon the size of the network.

7. Zero-price products

Traditional price elasticity is difficult to apply.

8. Monopoly pricing

The Cellophane fallacy can produce misleading elasticity estimates.

9. Multi-product firms

A firm's pricing decisions may involve complex portfolio effects.

10. Capacity constraints

Actual switching may be limited by supply rather than demand.

30. Relationship Between Elasticity and Market Power

Elasticity is closely related to the ability of a firm to exercise market power.

A simplified Lerner index relationship is:

P−MCP=−1Ed\frac{P-MC}{P}=-\frac{1}{E_d}

where:

PP = price;

MCMC = marginal cost;

EdE_d = own-price elasticity of demand.

The relationship indicates that, under simplified assumptions, less elastic demand permits a larger price-cost margin.

Thus:

Lower elasticity generally permits greater pricing power.

However, the formula is not a substitute for a full market-power analysis. Real markets involve multi-product firms, strategic interaction, dynamic competition and differentiated products.

31. Elasticity and Merger Control

Elasticity estimation is particularly useful in merger cases.

If merging firms sell close substitutes, the merger may eliminate substantial competitive pressure.

For example:

Firm A sells Product A;

Firm B sells Product B;

consumers frequently switch between A and B.

A merger between A and B may therefore substantially increase the merged firm's ability to raise prices.

Diversion ratios and elasticity estimates can help quantify this concern.

This is especially important in unilateral-effects analysis.

32. Elasticity and Coordinated Effects

Elasticity also affects the possibility of coordinated conduct.

If customers can easily switch to alternative suppliers, cartel members may find coordination difficult.

If demand is highly inelastic and firms have substantial market shares, coordinated price increases may be easier to sustain.

Other relevant factors include:

transparency;

number of competitors;

product homogeneity;

frequency of interaction;

capacity;

detection mechanisms;

retaliation possibilities.

33. Elasticity in Procurement Markets

In public procurement, elasticity may be analysed differently.

A procuring authority may have only a few viable suppliers.

If the procurement price rises, the buyer may not have practical alternatives because:

qualification requirements are strict;

switching suppliers takes time;

certification is expensive;

procurement rules limit substitution;

supply is geographically concentrated.

This may make the buyer's demand relatively inelastic.

Conversely, a buyer capable of quickly replacing suppliers can exert significant countervailing power.

34. Elasticity and Buyer Power

Elasticity also operates in reverse.

A powerful buyer may have a highly elastic demand for an individual supplier's output.

If Supplier A increases its price, the buyer can immediately switch to Suppliers B, C and D.

This constrains Supplier A.

Thus:

Elasticity can be evidence not only of seller-side market power but also of buyer-side bargaining power.

This is particularly relevant in:

agricultural procurement;

labour markets;

manufacturing inputs;

retail supply chains;

logistics;

digital advertising.

35. Overall Legal Test

In practical competition-law analysis, elasticity should generally be integrated into the following sequence:

Step 1 — Identify the candidate product

Determine the product or service allegedly constituting a market.

Step 2 — Identify substitutes

Examine consumer switching behaviour.

Step 3 — Estimate demand response

Calculate or infer own-price and cross-price elasticity.

Step 4 — Apply the hypothetical monopolist test

Ask whether a SSNIP would be profitable.

Step 5 — Expand the candidate market

Add sufficiently close substitutes if the SSNIP is unprofitable.

Step 6 — Consider supply substitution

Determine whether suppliers can rapidly switch production.

Step 7 — Define geography

Examine geographic switching and transport constraints.

Step 8 — Test robustness

Consider:

switching costs;

network effects;

capacity;

regulation;

quality;

innovation;

zero-price services.

Step 9 — Check for the Cellophane problem

Ensure that observed elasticity is not simply a consequence of an already supracompetitive price.

36. Key Case-Law Principles at a Glance

37. Conclusion

Elasticity estimation is an important economic tool for market definition, but it is not itself the legal definition of a market.

Its central contribution is to measure the extent to which customers or suppliers respond to changes in competitive conditions. High cross-price elasticity can indicate strong substitution, while low own-price elasticity can indicate market power.

However, elasticity must be interpreted together with:

the SSNIP/hypothetical-monopolist framework;

reasonable interchangeability;

customer switching;

supply substitution;

geographic constraints;

switching costs;

network effects;

capacity constraints;

innovation;

quality competition;

the Cellophane fallacy.

The most important lesson from the case law is therefore that market definition is an economic and legal exercise, not a purely mathematical one. Elasticity estimates provide evidence about competitive constraints, but courts and competition authorities must determine whether those constraints are sufficiently immediate, effective and sustainable to belong within the relevant market.