A Critical Analysis of Critical Loss Analysis 

Daniel P. O’Brien and Abraham L. Wickelgren*

May 23, 2003 

Abstract 

Critical loss analysis is often used to argue that firms with large margins have more to lose from 

a reduction in sales and hence are less likely to increase prices. This argument ignores the 

implication of economic theory that profit-maximizing competitors that do not coordinate their 

pricing only have large margins if their customers are not very price sensitive. We explore the 

implications of critical loss analysis using an internally consistent model of oligopoly. We show 

that for a given degree of substitutability between the merging firms’ products, firms with larger 

pre-merger margins will raise prices more than firms with smaller margins. This reinforces the 

traditional view that mergers are more likely to harm consumers when the merging firms have 

greater market power, as measured by their margins. We also derive internally consistent 

formulas for evaluating the profitability of price increases when defining markets and evaluating 

unilateral competitive effects. 

I. Introduction 

Critical loss analysis is a widely-used technique in antitrust practice.1 The basic idea is 

simple. One asks: “given a price increase of X percent,2 what would the percentage loss in unit 

sales have to be to make the price increase unprofitable?” This loss is referred to as the “critical 

loss for an X-percent price increase.” If the actual loss is less than the critical loss, the price 

 

*

 The authors are economists at the U.S. Federal Trade Commission. Patrick DeGraba, Alan Frankel, Ezra 

Friedman, Jerry Hausman, Stephen Holland, Dan Hosken, David Scheffman, David Schmidt, Carl Shapiro, Mike 

Vita and Charlotte Wojcik provided many useful comments and suggestions. The views in this article are those of 

the authors and do not necessarily reflect those of the Federal Trade Commission or any individual Commissioner. 

1

 The use of critical loss analysis was first suggested by Barry C. Harris and Joseph J. Simons, “Focusing Market 

Definition: How Much Substitution is Necessary?” Research in Law and Economics, v. 12, 1989, p.207-226. Since 

it was proposed, it has appeared in numerous White Papers presented to the antitrust agencies, numerous pre-trial 

affidavits, and expert testimony offered on behalf of antitrust defendants. 

2

 The analysis applies equally well for any potential price increase. 
2

increase would pay. Otherwise it would not. 

The most common uses of critical loss analysis are to define relevant markets and assess 

the competitive effects of mergers. For example, experts representing merging parties often use 

this technique to argue that where margins are high, the product market must be broader than the 

government contends. The argument is that the larger are the margins, the greater is the 

reduction in profits from sales lost after a price increase. Therefore, it takes a smaller critical 

loss to make a given price increase by a hypothetical monopolist unprofitable. The experts then 

argue that the actual loss from a 5 percent price increase would surely exceed the critical loss, 

implying that the relevant market must include substitutes that are not included in the 

government’s alleged market.3

 

Similar logic is often used to argue that a merged firm would not have an incentive to 

increase price by a given amount following a merger. Again, the argument is that the larger is 

the merging firm’s margin, the less likely it is that a given price increase would be profitable. 

Critical loss analysis is simple and has a degree of intuitive appeal. Unfortunately, the 

standard way that critical loss analysis is applied (henceforth, “standard critical loss analysis”) 

ignores two key points, often leading to inconsistent logic and erroneous conclusions. First, 

standard critical loss analysis fails to recognize that a firm’s margin provides information about 

the magnitude of the sales it is likely to lose from a price increase. If pre-merger prices are 

chosen to maximize profits, higher margins typically imply that customers are not very price 

sensitive (otherwise, a firm could substantially increase its sales by making a small price cut, 

 

3

 The FTC/DOJ Merger Guidelines define a product market as the narrowest set of products such that a hypothetical 

profit-maximizing monopolist would raise price a small but significant amount. U.S. Dep’t of Justice and Federal 

Trade Comm’n, Horizontal Merger Guidelines, §1.1 (1992, rev. 1997). For a discussion of the use of demand 

elasticities in defining antitrust markets, See Werden, Gregory, “Demand Elasticities in Antitrust Analysis,” 

Antitrust Law Journal, 66, 363, 1998. 
3

which would imply that the current price is not profit-maximizing).4

 This means that when 

margins are larger, a price increase will usually result in fewer lost sales than when margins are 

smaller. In short, the argument that a large percentage of sales would be lost in the event of a 

price increase is typically inconsistent with the existence of large pre-merger margins for profit 

maximizing firms. 

A second fundamental error of the standard critical loss analysis is that it ignores the 

importance of the degree of substitutability (e.g., the cross elasticities of demand or diversion 

ratios) among the products of the firm considering the price increase. The greater the cross 

elasticities, the more the firm will profit from increasing the price of one product because it will 

capture a larger percentage of the lost sales through increases in the sales of its other products. 

As an extreme example, consider a merger that would combine two products that have zero or 

very low cross elasticities between each other. A post-merger price increase on one of the 

products would not significantly raise the sales of the other, so the merger provides little or no 

incentive to raise price. On the other hand, suppose the merging firms have very high cross 

elasticities between each other. In this case, a price increase for one of the merging products 

results in substantial sales diverted to the other product, increasing the merged firm’s profits. If 

margins are high, so that the diverted sales are highly profitable, the merged firm will have a 

relatively higher incentive to raise price absent offsetting entry, product repositioning, or 

efficiency gains. 

In the “hypothetical monopolist test” outlined in the Merger Guidelines for defining 

markets, the hypothetical monopolist always controls multiple products. The question of 

whether a price increase would be profitable cannot be answered without accounting for the 

 

4

 This assumes that the firms are not coordinating their behavior. If the firms are tacitly colluding, then margins 

could be large even when each firm’s own demand is fairly elastic. 
4

cross elasticities among the products under the monopolist’s control. Similarly, since a merger 

alters the set of products under a firm’s control, the analyst must account for cross elasticities 

when assessing the profitability of a post-merger price increase. However, critical loss analysts 

often fail to do this. 

 The important roles of the margin/elasticity relationship and cross elasticities for optimal 

pricing are stressed in economics and business school courses on pricing and strategy. However, 

the implications of these factors for critical loss analysis are not widely appreciated in the 

antitrust community. The purpose of this article is to clarify the role of these factors in firms’ 

pricing decisions and to explore rigorously the implications of these factors for critical loss 

analysis.5

We examine critical loss analysis using a standard Bertrand pricing model, which is the 

most widely-used framework in economics for modeling oligopoly among price-setting firms 

that do not coordinate their behavior. We focus on differentiated products, although the central 

result that high margins tend to make post-merger price increases more likely also emerges from 

standard theories of competition among producers of homogenous products.6 The analysis is 

applicable both to market definition, where the merger would be a hypothetical merger to 

monopoly, and competitive effects analysis, where the question is whether it would be profitable 

for the merging firms to increase price after the merger. By explicitly modeling oligopoly price-

 

5

 We should note that our critique does not invalidate the critical loss formula derived in Harris and Simons (op. cit.) 

as an algebraic statement about the loss necessary to make a given price increase unprofitable. Our criticism is 

directed at the application of the formula without regard to whether the assumptions and conclusions in the 

application are consistent with standard economic theory. 

6

 If the products in the industry are homogenous, then large margins are often associated with capacity constraints. 

In this case, the fringe supply elasticity plays a role analogous to cross elasticities, i.e., it affects the amount of 

substitution away from the hypothetical monopolist (or the merging firms) in the event of a price increase or 

quantity decrease. Thus, the profitability of a price increase depends in part on the elasticity of the fringe supply. 
5

setting and carrying out an internally consistent analysis within this framework, we obtain the 

following results: (1) For a given degree of product substitutability between the products (that is, 

a given cross-price elasticity or diversion ratio), larger margins make it less likely that the actual 

loss will exceed the critical loss from a price increase.7

 (2) Under linear and constant elasticity 

demand, simple conditions determine when the actual loss from a price increase will exceed the 

critical loss. These conditions require estimation of the cross-price elasticities (or diversion 

ratios) between the products of the merging parties, in addition to the merging firms’ margins. 

An implication for antitrust practice is that testimony about the demand curve is most helpful 

when it focuses on the substitutability (cross-price elasticities or diversion ratios) between the 

merging products.8

 

 Since critical loss analysis has become such a widely used tool, our criticism might be 

viewed skeptically by antitrust practitioners. In anticipation of this skepticism, we want to state 

up front the assumptions that underlie our key results. Our most important result is that higher 

margins typically make it more likely that a price increase by merging firms will be profitable. 

This result requires four main assumptions: (1) firms attempt to maximize profits before and 

after the merger; (2) the merger enhances the degree of coordination between the merging firms’ 

products; (3) the response of consumers to a small price increase is not significantly greater than 

their response to a small price decrease; and (4) the cost of a small increase in output is not 

 

7

 Of course, high margins probably mean that cross-price elasticities are not too large; the point is that one needs to 

know both own- and cross-price elasticities. 

8

 Other authors have noted the pitfalls that can arise if critical loss analysis is not applied within a consistent 

economic framework. In a recent article that we learned about while this article was being reviewed, Michael Katz 

and Carl Shapiro present a critique that makes many of the same points that we make here. See Katz, Michael and 

Carl Shapiro, “Critical Loss: Let’s Tell the Whole Story,” forthcoming in Antitrust Magazine. See also Langenfeld 

James and Wenquing Li, “Critical Loss Analysis in Evaluating Mergers,” The Antitrust Bulletin, Summer 2001, pp. 

299-337; Danger, Kenneth L. and H.E. Frech III, “Critical Thinking about `Critical Loss’ in Antitrust,” The Antitrust 

Bulletin, Summer 2001, pp. 339-355, and Werden, Gregory J., “Beyond Critical Loss: Tailoring Applications of the 
6

significantly greater than the cost savings from a small reduction in output. 

Assumptions 1 and 2 are core premises of competition policy toward horizontal mergers. 

The assumption that profit maximization “provides a good first approximation in describing 

business behavior”9

 is a basic postulate of most of economic analysis. Profit maximization is 

also a key assumption of critical loss analysis, which involves balancing the gains and losses 

from a price increase. The assumption that mergers make coordination more likely may not hold 

in some cases if firms have discovered ways to coordinate without merging. However, even in 

these cases, coordination has a chance to break down if the firms are kept separate but will not 

break down if they merge. 

 Assumptions 3 and 4 amount to assuming away “kinks” in the firms’ demand and cost 

curves, so that the responsiveness of each curve to a small increase in price is similar to the 

responsiveness to a small price decrease. Economic theory does not rule out such kinks. 

Economists usually assume that cost and demand curves are smooth rather than kinked, in part 

because this simplifies the analysis, but also because this assumption is usually reasonable for 

broad ranges of prices and quantities. For example, if the products in question have many 

heterogeneous customers, then aggregate demand curves will be relatively smooth. Similarly, if 

the inputs used in production (labor, supplies, capital equipment) are scaleable, then cost curves 

will be smooth as well. Competition policy is built partly on presumptions that flow from 

economic analysis, and our view is that Assumptions 3 and 4 are the “normal” cases appropriate 

for establishing such presumptions. Of course, if credible evidence that these assumptions are 

 Hypothetical Monopolist Paradigm,” mimeo, U.S. Department of Justice, Antitrust Division, Economic Analysis 

Group, July 2002. 

 

9

 Scherer, F.M. Industrial Markett Structure and Economic Performance, 2nd ed., Chicago: Rand-McNally, 1980, p. 

41. 
7

violated presents itself, it should be incorporated into the analysis of the effects of a merger. We 

discuss some ways that these assumptions may be violated in Section III.B. 

In our formal analysis we make additional assumptions both for expositional purposes 

and to derive formulas for specific cases. Our formulas assume constant marginal cost, just as 

standard critical loss analysis does. We present formulas that apply only to the special cases of 

symmetric Bertrand competition and linear or constant elasticity demand. However, one could 

obtain similar qualitative results (but different formulas) under different assumptions about the 

nature of rivalry, demand and costs. While cross elasticities play a key role under differentiated 

Bertrand competition, the elasticity of fringe supply becomes important under quantity 

competition with homogenous products (either Cournot competition, or competition between a 

dominant firm and a competitive fringe). Different assumptions about demand and costs would 

affect the quantitative analysis but would not affect our main conclusions. 

 The remainder of this article is organized as follows. Section II presents the standard 

critical loss analysis for a hypothetical merger. Section III evaluates the standard critical loss 

analysis using elementary economic theory and shows how to modify the analysis to make it 

internally consistent. Section IV discusses two recent antitrust cases in which the standard 

critical loss analysis was applied and shows how the conclusions change if an internally 

consistent approach is used. Section V concludes with a discussion of the role of critical loss 

analysis in antitrust practice. 

II. The Standard Critical Loss Analysis – A Typical Example 

 For the sake of discussion, imagine two symmetric firms, A and B, each selling a single 
8

differentiated product in competition with several other firms.10 To simplify the analysis, we 

assume linear demand and constant marginal cost. We also assume that each firm chooses its 

own price unilaterally to maximize profits prior to the merger. 

Suppose firms A and B propose to merge. The government believes that the appropriate 

product market for analyzing the merger includes only products A and B. The merging firms 

contend that the market is broader. In support of their claim, the merging firms’ consultants 

present a standard critical loss analysis. They argue as follows: 

The percentage margin earned by firms A and B is 60 percent. Thus, the “critical loss” in 

unit sales above which a 5 percent price increase would be unprofitable is 7.7 percent. 

The testimony indicates that a 5-percent increase in the prices of products A and B would 

likely result in a loss in unit sales of A and B of at least 10 percent, which exceeds the 

critical loss. This means that a 5 percent price increase would not be profitable, so the 

relevant product market must include other products in addition to products A and B. 

This argument is typical of the critical loss analyses presented in numerous antitrust cases. In 

order to evaluate it, we first need to understand how the critical loss is determined. 

The critical loss for an X-percent price increase is the percentage reduction in quantity 

required for the price increase to leave profits unchanged.11 Calculating the critical loss requires 

balancing two effects: 1) a given price increase raises the profit margin earned on all units that 

are sold, but 2) it also reduces the quantity demanded resulting in fewer units being sold. The 

critical loss is the percentage reduction in quantity such that these two effects just balance. If the 

 

10 By symmetric we mean that firms A and B have the same cost functions and symmetric, but potentially 

differentiated, demand. Symmetric demand means that the firms will sell same amount if they charge the same 

prices, and that firm A’s demand at one pair of prices is the same as what firm B’s demand would be if their prices 

were interchanged. 

11 The 1992 Merger Guidelines define markets by asking whether a profit-maximizing monopolist would impose a 

“small but significant and non-transitory price increase” (SSNIP). The critical loss calculation, by contrast, 

addresses the question of whether a particular SSNIP, not necessarily the profit-maximizing one, yields higher profit 

than the pre-merger price. A rough approximation (exact for linear demand) is that the profit-maximizing price 

increase is half as much as the price increase that leaves profits unchanged. For example, a 5 percent price increase 

would be optimal (approximately) if a 10 percent price increase leaves profits unchanged. 
9

reduction in unit sales is greater than the critical loss, then the price increase will reduce profits. 

If the reduction in unit sales is less then the critical loss, the price increase will increase profits. 

 A small amount of notation is useful to describe this calculation. Suppose that firms A 

and B both produce at constant unit cost c. The pre-merger price of products A and B is p, and 

the pre-merger total quantity of A and B is q. Denote a given price increase for both products A 

and B by Dp and the resulting change in the total quantity of A and B by Dq. Since the quantity 

demanded falls with price, the change in quantity, Dq, is a negative number. 

With this notation, the critical loss calculation is easy to describe. The benefit to the 

hypothetical monopolist from a price increase is the amount of the price increase times the 

quantity that will be sold at the new price, i.e., Dp[q+Dq]. The cost to monopolist of the price 

increase is equal to the pre-merger margin times the quantity reduction caused by the price 

increase, i.e., -(p-c)Dq. The benefit and cost of the price increase just balance if 

(1) 













 = ∆ + ∆ = − − ∆ = 















priceincrease

Cost of

p q q p c q priceincrease

Benefit of [ . ] ( )

The formula for the critical loss is found by dividing both sides of this equation by pq. This 

gives 

(2) 

q

q

p

p c

q

q

p

p ∆















 − = − 



 



 ∆

+

∆ 1 . 

The critical loss is the percentage reduction in quantity, -Dq/q, that satisfies condition (2).12 

Solving for the critical loss gives 

(3) -

p p m

p p Critical Loss

q

q

∆ +

∆ = = ∆

/

/

 

12 Throughout the article we associate percentages with decimal equivalents. For example, if Dq/q = .10, the 

percentage reduction in quantity would be 10 percent. 
10

where m = (p-c)/p is the margin measured as a percentage of the price. Since Dp/p is just the 

percentage price increase, condition (3) implies that the critical loss for an X-percent price 

increase is 

(4) X m

X Critical Loss

+ = . 

The formula for the critical loss in (4) shows that for a given price increase of X percent, 

the critical loss is smaller the larger is the margin. Intuitively, the larger is the margin, the 

greater the profit lost from a given reduction in quantity, so the smaller the reduction in quantity 

required for a given price increase to be unprofitable. 

If the margin is 60 percent, as the merging firms in our example contend, the critical loss 

from a 5 percent price increase is 

(5) .077 .05 .6

.05

≅

+

Critical Loss = , 

or about 7.7 percent. In the example, the merging firms argue that the unit sales lost from a 5 

percent price increase on both products would be at least 10 percent. Since this loss exceeds the 

critical loss, they conclude that a 5 percent price increase would not be profitable. The 

implication they draw is that the price increase would cause enough customers to switch to other 

products that the price increase would be unprofitable, suggesting that the relevant market must 

include other products in addition to products A and B. 

III. Economics of Critical Loss 

A. Inconsistency of the Standard Critical Loss Analysis 

We will now analyze the merging firms’ argument using standard economic theory. At 

the outset, we should note there is nothing wrong with the standard critical loss calculation itself. 
11

The calculation is simply algebra, and formula (4) is certainly correct. The problem arises in the 

interpretation of (4) in light of evidence about the actual loss from a given price increase. 

Economic theory tells us quite a bit about the relationship between the actual loss from a price 

increase and the critical loss expressed in (4). An antitrust argument that is grounded in 

economics must recognize this relationship when evaluating evidence about the actual loss from 

a price increase. We will show that, by ignoring this relationship, the standard critical loss 

analysis is internally inconsistent and often leads to faulty conclusions. 

 We begin our critique by describing what economic theory tells us about the actual loss 

in unit sales from a given price increase. It is helpful conceptually to think about breaking the 

price increase into two steps involving first an increase in the price of product A and then an 

equivalent increase in the price of product B.13 A price increase of X percent for product A 

causes a reduction in the quantity demanded for product A. Because products A and B are 

substitutes, it also causes an increase in the demand for product B. Denote the own elasticity of 

demand for product A as EOwn and the cross elasticity of demand for product B with respect to 

the price of product A as ECross.

14 An X-percent increase in the price of product A causes the unit 

sales of product A to fall by the amount of the price increase times the own elasticity of demand, 

 

13 If the firms have multiple products, then one needs to consider how increases in the prices of each product affect 

the demand for all of the products of both firms. The analysis is similar, though more complex, and the qualitative 

conclusions for critical loss analysis are unchanged. 

14 The own elasticity of demand for product A is the percentage reduction in unit sales for product A divided by the 

percentage increase in its price for a small increase in price. The cross elasticity of demand for product B with 

respect to the price of product A is the percentage increase in unit sales for product B divided by the percentage 

increase in the price of product A for a small increase in price. We follow the convention of expressing own 

elasticities as positive numbers even though the change in own quantity from a price increase is negative. 

Technically, these definitions are for “point” elasticities corresponding to small price changes, which generally may 

differ from “arc” elasticities appropriate for evaluating the effects of larger price increases like those contemplated 

by the merger guidelines (e.g., 5 and 10 percent). While arc elasticities are usually defined using the average price 

and quantity as the base, we use the initial price and quantity as the base since the merger guidelines measure 

percentage price increases using initial prices as the base. With arc elasticities defined this way, the point and arc 

elasticities are equivalent under the special case of linear demand. 
12

i.e., by XEOwn percent. Similarly, the price increase causes the unit sales of product B to rise by 

the amount of the price increase times the cross elasticity of demand, or XECross percent. Since 

products A and B are symmetric in this example, an X-percent increase in the price of product B 

causes the unit sales of product B to fall by XEOwn percent and the unit sales of product A to rise 

by XECross percent. Combining these effects, a price increase of X percent for both products A 

and B causes a reduction in the unit sales of X[EOwn - ECross] percent for both products. So the 

actual loss in percentage terms experienced by the hypothetical monopolist from an X-percent 

price increase is 

(6) ] [ Own Cross Actual Loss = X E − E .

15

 One more step is necessary before we can assess the consistency of standard critical loss 

analysis. The pre-merger margins of firms A and B provide information about the extent to 

which consumers are willing to substitute away from their products. A profit maximizing firm 

raises price to the level at which the benefit of an additional price increase on each unit sold is 

just offset by the reduction in sales due to the additional price increase. Denote the quantity of 

product A by q

A

, the increase in the price of product A by Dp

A

, and the associated change in the 

quantity of product A by Dq

A

 (note that Dq

A

 is negative). Profit maximization requires that firm 

A raise price to the point where the gains from an additional price increase, Dp

A

[q

A

+Dq

A

], just 

offset the cost of the price increase, -(p-c)Dq

A

. That is 

(7) 













 = ∆ + ∆ = − − ∆ = 















priceincrease

Cost of

p q q p c q priceincrease

Benefit of A A A A A [ . ] ( )

Note that the profit maximization condition (7) is the same type of balancing condition as that 

 

15 Adding the percentage changes in own and cross effects this way is permitted by the assumption that products A 

and B are symmetric. The intuition for the inconsistency in standard critical loss analysis in the symmetric case 

carries over to the asymmetric case. 
13

used in the critical loss equation (1), except that it must hold for each firm individually. If we 

divide both sides of (7) by q

A

Dp

A

/ p

A

, the condition can be rewritten as 

(8) 



 



 ∆ = + A

A

Own q

q

E

m 1 1

where EOwn=-(Dq

A

/q

A

)/(Dp

A

/ p

A

) is the own-elasticity of demand for product A. If firm A is 

maximizing its profits, the balancing condition (8) must hold for an arbitrarily small increase in 

price. For a small price increase, Dq

A

 is approximately zero. So the profit maximization 

condition boils down to 

(9) Own E

m

1 = . 

Condition (9) is just the inverse elasticity rule for profit maximization familiar from elementary 

microeconomic theory. It is derived from the same type of balancing condition as that used to 

derive the critical loss. Since the calculations are so similar, it should not be surprising that the 

assumption of profit maximization has strong implications for critical loss analysis, as we now 

show. 

 Substituting (9) into (6), the actual loss experienced by the hypothetical monopolist from 

an X-percent price increase is 

(10) 



 



 = − Cross E

m

Actual Loss X 1 .

16 

We can use condition (10) to evaluate the merging firms’ critical loss analysis in our example. A 

price increase of X percent for products A and B will be unprofitable if the actual loss exceeds 

the critical loss, that is, if 

 

16 Again, because the point and arc elasticities are equal under linear demand, we can use the relationship between 

the margin and the point elasticity to substitute for the arc elasticity of demand. 
14

(11) Critical Loss

X m

X E

m

Actual Loss X Cross = +

>



 



 = − 1

After a bit of algebra, we find that the actual loss exceeds the critical loss if and only if 

(12) ( )

X Critical Loss Cross E

mX m m

= >

+ . 

Notice that the left-hand-side of condition (12) falls as the margin increases. This implies 

the following important result: holding cross elasticities between the merging firms constant, 

a given price increase is more likely to be profitable the larger is the margin.17 This 

implication of standard microeconomic theory is exactly the opposite of that implied by the 

standard critical loss analysis, though it is completely in line with the conventional wisdom that 

mergers tend to be more problematic in more concentrated industries. 

An equivalent way to express condition (12) that is sometimes easier to interpret is in 

terms of the diversion ratio between A and B, which is the fraction of sales lost by A when it 

raises price that are recaptured by B.18 Under symmetry, the cross elasticity is equal to the 

diversion ratio divided by the margin. Substituting this relationship into condition (12), we have 

that (with symmetric demand) a price increase is unprofitable if and only if 

(13) ( )

X Critical Loss Diversion Ratio

X m

= >

+ . 

 

17 Technical readers may wonder what implicit assumptions are being made about other cross elasticities in making 

this statement. To be precise, suppose consumers buy three products: A, B, and C. Denote the elasticity (or cross 

elasticity) of demand for product i with respect to the price of product j as Eij, and denote the consumers’ budget 

share of product i as si. The microeconomic theory of the consumer implies that budget shares and elasticities are 

related according to the equation (1-EAA)sA + EBA sB + ECA sC = 0. This implies that for any given cross elasticity 

EBA, a lower value of EAA (a higher margin) is associated with a smaller cross elasticity between products C and A 

and/or a larger budget share for product A. 

 

18 Formally, the diversion ratio from A to B can be defined as D=(qB

/qA)(ECross/EOwn). See Shapiro, Carl, “Mergers 

with Differentiated Products,” Antitrust Magazine, Spring 1996, p. 23-30. Using this definition and the margin 

elasticity relationship m=1/EOwn, it is straightforward to translate the cross elasticity condition into the diversion 

ratio condition presented in the text. 

 
15

Recall that the merging firms in our example argued that the actual loss from a 5 percent 

price increase for both products would be 10 percent or more. However, if we accept the 

merging firms’ assumption that the margin is 60 percent, condition (10) implies that the actual 

loss is 

(14) 



 



 = − Cross Actual Loss E .6

1 . 05

 Cross = .083 −.05E

 < .083, 

or less than 8.3 percent.19 We conclude that if firms A and B were pricing unilaterally to 

maximize their own profits prior to the proposed merger, and if the margin is correctly 

measured,20 then the actual loss from a 5 percent price increase could not be as high as the 

merging firms contend. 

 This logical error appears repeatedly in the standard critical loss analysis. The key 

mistake is the failure to recognize that margins will be high only if customers are not very 

sensitive to changes in price, i.e., only if the actual loss from an additional price increase would 

be small. We know this from the margin elasticity relationship implied by the assumption of 

profit maximization, m=1/EOwn, or EOwn=1/m. This condition implies that the actual loss from a 

price increase by an individual firm varies inversely with the margin. The actual loss for the 

hypothetical monopolist must be smaller than the loss for an individual firm because some of the 

lost sales are recaptured through increased sales of substitute products. For a given cross 

elasticity between products A and B, the recapture rate is independent of the margin. Therefore, 

 

19 The last inequality in (14) is true because the cross elasticity is positive for substitute goods. 

20 We assume throughout this analysis that margins are appropriately measured, as this is a necessary condition for 

critical loss analysis to be valid. Of course, an inconsistency between the actual loss and the margin could be 

attributable to an error in either number. 
16

the actual loss that a hypothetical monopolist experiences from a given price increase is also 

smaller the larger is the margin. 

 In our example, the actual loss to the hypothetical monopolist from a 5 percent price 

increase cannot exceed 8.3 percent. This is the actual loss when the cross elasticity between 

products A and B is zero (to see this, set ECross=0 in (14)). Note that this amount is greater than 

the critical loss of 7.7 percent in the example, so that it is still possible for the actual loss to 

exceed the critical loss and for the conclusions of the critical loss analysis to be correct. 

However, the actual loss exceeds the critical loss in the example only if the cross elasticity is 

quite small, i.e., only if 

(15) Actual Loss E Critical Loss Cross = + = − > .05 .6

.05 ] .61 . . 05[

Condition (15) is true only if ECross < .13. This is a fairly low cross elasticity, indicating that 

products A and B are not especially close substitutes. For example, the diversion ratio from A to 

B would have to be less than 8 percent. Again, this is in line with standard intuition: in a 

concentrated industry with high margins and significant diversion ratios, a merger is likely to be 

anticompetitive in the absence of offsetting efficiencies, entry, or product repositioning. 

 Although the discussion to this point has focused on the effects of combining two 

products, it should be apparent that the analysis extends straightforwardly to the effects of 

combining any number of symmetric products. In particular, an X-percent price increase for N 

symmetric products is profitable if the sum of the cross elasticities between any one of the N 

products and the N-1 rival products in the group exceeds the critical cross elasticity, or if the sum

of the diversion ratios exceeds the critical diversion ratio.21 Formulas 6 through 15 are still valid, 

 

21 The analog of equation (6) for the N-product case is Actual Loss = X[EOwn – (N-1)ECross]. The sum of the 

diversion ratios from one product to the other N-1 products is the “aggregate diversion ratio” defined by Katz and 
17

but the cross elasticity ECross is interpreted as the sum of the cross elasticities between one of the 

products and the other products in the group. Similarly, the diversion ratio is interpreted as the 

“aggregate diversion ratio” from one product to all the others in the group. Using this 

interpretation, it is possible to use conditions (12) and (13) to conduct the hypothetical 

monopolist test for more than two products. The formulas are exact when products are 

symmetric. A more complex calculation is required for asymmetric cases. However, a 

conservative lower bound on the critical cross elasticity and diversion ratio can be found by 

using the smallest margin of all the products in the group to evaluate the formulas. 

Table 1 presents the critical cross elasticities and critical diversion ratios below which a 

price increase for a group of products is unprofitable given different pre-merger margins. 

Referring to our earlier example in which the margin was 60 percent, the table shows that a 5 

percent price increase by a hypothetical monopolist of N products would be unprofitable if the 

sum of the cross elasticities between one of the products and the other products in the group is 

less than .13, or if the aggregate diversion ratio (the sum of the diversion ratios from one product 

to the others in the group) is less than 7.7 percent. More generally, Table 1 shows that the 

critical cross elasticity and diversion ratio is smaller the higher is the margin, which is the main 

point of this article. 

 Shapiro, op. cit. Condition (13) shows that a particular price increase will be unprofitable if the aggregate diversion 

ratio is less then the critical loss, as Katz and Shapiro emphasize in their article. 
18

Table 1: Critical Cross Elasticities and Diversion Ratios for the Profitability of an 

Increase in the Price of N Symmetric Products – Linear Demand 

1% Price Increase 5% Price Increase 10% Price Increase 

Margin 

Critical 

Cross 

Elasticity 

Critical 

Diversion 

Ratio 

Critical 

Cross 

Elasticity 

Critical 

Diversion 

Ratio 

Critical 

Cross 

Elasticity 

Critical 

Diversion 

Ratio 

10% 0.91 9.1% 3.33 33.3% 5.00 50.0% 

15% 0.42 6.3% 1.67 25.0% 2.67 40.0% 

20% 0.24 4.8% 1.00 20.0% 1.67 33.3% 

25% 0.15 3.8% 0.67 16.7% 1.14 28.6% 

30% 0.11 3.2% 0.48 14.3% 0.83 25.0% 

35% 0.08 2.8% 0.36 12.5% 0.63 22.2% 

40% 0.06 2.4% 0.28 11.1% 0.50 20.0% 

45% 0.05 2.2% 0.22 10.0% 0.40 18.2% 

50% 0.04 2.0% 0.18 9.1% 0.33 16.7% 

55% 0.03 1.8% 0.15 8.3% 0.28 15.4% 

60% 0.03 1.6% 0.13 7.7% 0.24 14.3% 

65% 0.02 1.5% 0.11 7.1% 0.21 13.3% 

70% 0.02 1.4% 0.10 6.7% 0.18 12.5% 

75% 0.02 1.3% 0.08 6.3% 0.16 11.8% 

80% 0.02 1.2% 0.07 5.9% 0.14 11.1% 

85% 0.01 1.2% 0.07 5.6% 0.12 10.5% 

90% 0.01 1.1% 0.06 5.3% 0.11 10.0% 

Note: For a price increase on N ≥ 2 products, the critical cross elasticity (critical diversion ratio) is 

compared with the sum of the cross elasticities (diversion ratios) between one product and each of the 

N-1 other products in the group. 

The critical cross elasticities and diversion ratios in Table 1 are applicable for the special 

case of linear (i.e., “straight line”) demand. Linear demand has the property that as the price 

increases, the own elasticity of demand rises, gradually dampening incentives for further price 

increases. It is worth pointing out that for many other demand curves used by antitrust 

economists (constant elasticity, logit, AIDS, semi-log), the elasticity does not rise as sharply with 

price as it does with linear demand. This means that the critical cross elasticity and diversion 

ratios are typically smaller under these other demand assumptions than they are for linear 

demand. 

 
19

Another important special case is constant elasticity demand, which assumes that the 

elasticity does not change with price. Table 2 presents the critical cross elasticities and diversion 

ratios for the constant elasticity case.22 The critical values are significantly lower in this case 

than they are under linear demand. This difference arises because the actual loss from a given 

price increase is smaller under constant elasticity demand than it is for linear demand given the 

same initial own-price elasticity. As for the case of linear demand, the critical cross elasticity 

and diversion ratio fall as the margin rises. This confirms our main point that a merger is more 

likely to result in higher prices the higher is the pre-merger margin. 

 

22 We explain here how the critical values in Table 2 were generated. For constant elasticity demand, unlike linear 

demand, point and arc elasticities are different. The constant (point) elasticity demand curve is 

1 2

Own Cross E E

q ap p − = . The arc own elasticity (in absolute value) is the percentage reduction in quantity divided by 

the percentage increase in price. This is given by the following formula: 

1 2 12

1 2

((1 ) )

( )

Own Cross Own Cross

Own Cross

E E EE

Own

E E

a X p p ap p arcE

X ap p

− −

−

+ − = −

Simplifying and imposing symmetry, this can be rewritten as follows: 

Own

E

Own E

X

X arcE

Own

≠ − + =

− 1 (1 )

A similar calculation yields the arc cross elasticity: 

Cross

E

Cross E

X

X arcE

Cross

≠

+ − = (1 ) 1

We can use the arc elasticities to rewrite the actual loss, equation (6), in terms of the point elasticities. 

Own Cross E E ActualLoss = 2 − (1+ X ) − (1+ X ) −

Because profit maximization implies that the margin is the inverse of the own point elasticity, we can write the 

actual loss as follows: 

Cross m E ActualLoss 2 (1 X ) (1 X ) 1/ = − + − + −

Equating the actual loss with the Critical Loss, X/(X+m), and solving for Cross

E , we find that the Actual Loss exceeds 

the Critical Loss if and only if: 

1/ ln(2 (1 ) )

ln(1 )

m

Cross

X X

X m E

X

− −+ −

+ <

+

This is the formula used to generate Table 2. 
20

Table 2: Critical Cross Elasticities and Diversion Ratios for the Profitability of an 

Increase in the Price of N Symmetric Products – Constant Elasticity Demand 

1% Price Increase 5% Price Increase 10% Price Increase 

Margin 

Critical 

Cross 

Elasticity 

Critical 

Diversion 

Ratio 

Critical 

Cross 

Elasticity 

Critical 

Diversion 

Ratio 

Critical 

Cross 

Elasticity 

Critical 

Diversion 

Ratio 

10% 0.38 3.8% 1.05 10.5% 1.14 11.4% 

15% 0.17 2.5% 0.56 8.4% 0.71 10.7% 

20% 0.09 1.8% 0.33 6.7% 0.47 9.4% 

25% 0.06 1.4% 0.22 5.4% 0.32 8.1% 

30% 0.04 1.1% 0.15 4.4% 0.23 6.9% 

35% 0.03 0.9% 0.10 3.7% 0.17 5.9% 

40% 0.02 0.7% 0.08 3.0% 0.13 5.0% 

45% 0.01 0.6% 0.06 2.5% 0.09 4.3% 

50% 0.01 0.5% 0.04 2.1% 0.07 3.6% 

55% 0.01 0.4% 0.03 1.8% 0.06 3.0% 

60% 0.01 0.3% 0.02 1.4% 0.04 2.5% 

65% 0.00 0.3% 0.02 1.2% 0.03 2.1% 

70% 0.00 0.2% 0.01 0.9% 0.02 1.7% 

75% 0.00 0.2% 0.01 0.7% 0.02 1.3% 

80% 0.00 0.1% 0.01 0.6% 0.01 1.0% 

85% 0.00 0.1% 0.00 0.4% 0.01 0.7% 

90% 0.00 0.1% 0.00 0.3% 0.01 0.5% 

Note: For a price increase on N ≥ 2 products, the critical cross elasticity (critical diversion ratio) is 

compared with the sum of the cross elasticities (diversion ratios) between one product and each of the 

N-1 other products in the group. 

 Readers will no doubt notice that the critical values in Tables 1 and 2 are quite different 

from each other. This shows that the profitability of a particular price increase is quite sensitive 

to the shape of the demand curve. While unfortunate, since in most cases the shape of the 

demand curve is unknown, this is unavoidable. It does suggest, however, that one should be 

cautious in using the critical values in Tables 1 and 2 to evaluate mergers. One way to approach 

this issue is to view Table 1 as “conservative” in predicting when mergers might be problematic, 

and to view Table 2 as “conservative” in the opposite sense of stopping mergers that have any 

chance of being problematic. Alternatively, if one does have information about the shape of the 

demand curve, the techniques in this article could be used to derive critical cross elasticities and 
21

diversion ratios for the profitability of different price increases.23

 

B. Can Critical Loss Analysis Be Consistent with Economic Theory? 

Our critique of standard critical loss analysis illustrates how to modify it to make it 

consistent with static Bertrand oligopoly theory, the most widely-used theory in economics to 

analyze price competition among imperfectly competitive firms that do not coordinate their 

pricing. The key predictions of this theory are given in conditions (12) and (13). The important 

factors for determining the profitability of a price increase are the pre-merger margin and the 

cross-elasticity of demand or diversion ratio. If the cross elasticity or diversion ratio is less than 

a critical value that varies inversely with the margin, then the price increase is not profitable. 

 The standard critical loss formula is an algebraic calculation that is not based on any 

assumptions about firms’ pre-merger behavior. Thus, standard critical loss analysis -- comparing 

the critical loss formula with evidence about the actual loss -- does not incorporate the 

consistency requirements of any economic theory. Under most economic theories, higher 

margins tend to be associated with lower own-price elasticities of demand. The idea is that it 

only makes sense for a firm to charge high prices (hence high margins) if its customers are not 

very price sensitive. Standard critical loss analysis effectively ignores this relationship. 

Therefore, standard critical loss analysis can be consistent with economic theory only in 

environments in which the usual inverse relationship between margins and own-price elasticities 

does not hold. 

 In the introduction, we described four key assumptions of our analysis, at least one of 

which would have to be violated for standard critical loss analysis to be consistent with 

 

23 Of course, if one knows the shape of the demand curve, one could simulate the profit-maximizing post-merger 

prices to examine the competitive effects of the merger. In our view, this is the best technique for evaluating the 

competitive effects of a merger. 
22

economic theory. One possibility is that firms fail to pursue profit maximization as their 

objectives. However, a basic premise of critical loss analysis is that firms do evaluate the 

profitability of a post-merger price increase. Thus, the failure of firms to maximize profits 

cannot be taken seriously as a justification for conducting standard critical loss analysis. 

 A second possibility is that firms engage in coordinated pricing prior to the merger, 

which yields higher margins than implied by the inverse elasticity rule, i.e., m > 1/EOwn. Premerger coordination is certainly a possibility in any merger situation, but standard critical loss 

analysis still suffers consistency problems in this case. One potential problem is the erroneous 

conclusion that markets are broad because a hypothetical monopolist who is already charging a 

monopoly price cannot profitably raise price further. One way to address this problem is by 

using non-collusive prices as the base for evaluating the profitability of a price increase. 

However, this places the analysis back into the framework we have developed, in which standard 

critical loss analysis suffers precisely the consistency problems we have described. A complete 

investigation of critical loss analysis under coordinated behavior would require an economic 

theory that permits coordination, predicts the degree of coordination prior the merger, and 

predicts how the degree of coordination would change with the merger. Such an analysis is 

beyond the scope of this article. However, it is worth noting that pre-merger coordination is 

usually viewed as grounds for blocking a merger. The economic logic for this view is that 

coordination is usually more likely to break down the less concentrated is the industry. 

 The other potential way that critical loss analysis can be consistent with economic theory 

is if the increase (decrease) in profits from a small increase in price differs significantly from the 

decrease (increase) in profits from a small reduction in price. This can occur if the demand or 

cost curves are kinked. 
23

 Consider first the case of kinked demand. If the reduction in quantity from a small price 

increase exceeds the increase in quantity from a small price decrease, then the firm’s own-price 

elasticity will be higher at prices above the prevailing price than it is at prices below this price. 

Facing this type of demand, it may pay a profit-maximizing firm to raise price up to the point of 

the kink, but then not raise price any further. In this situation, the inverse elasticity relationship 

may not hold, and it is possible that m > 1/EOwn (recall EOwn is the elasticity defined for an 

increase in price from the prevailing level). If the margin exceeds the inverse of the own-price 

elasticity at the profit-maximizing price, then the critical cross elasticities and diversion ratios 

will be higher than the values reported in Tables 1 and 2. Further, for given values of the ownand cross-price elasticities, the higher is the margin, the smaller is the maximum price increase 

that will be profitable. This is consistent with the prediction of standard critical loss analysis. 

 A kink in marginal cost can have similar effects. For example, suppose that the merging 

firms are currently capacity constrained, so that the marginal cost of expanding output is very 

high, but the cost savings from reducing output are quite low. In this case, the margin earned on 

the units sold up to capacity can be quite high, potentially higher than the inverse of the own 

elasticity. As with the kinked demand example, the inverse elasticity relationship may not hold 

in the short run (until capacity can be adjusted), and higher margins can be consistent with 

smaller price increases by a hypothetical monopolist. 

 By focusing on the “standard” cases of smooth demand and costs, we do not mean to 

suggest that kinked demand or costs would never be important to consider when analyzing the 

effects of a merger. Economic theory certainly does not rule these cases out. For example, a 

kinked demand curve may exist for a product if there is a common threshold price above which a 

significant fraction of customers will substitute to another product or to another firm in a more 
24

distant geographic area. On the other hand, if customers are numerous and have heterogeneous 

preferences, they will substitute to other products at a variety of different prices. In this case the 

aggregate demand across all customers will look relatively smooth because customers will 

gradually substitute to other products as price is increased. 

Kinked costs of the type described above may arise in the short run in some industries in 

which plants typically operate at capacity and expansion is expensive. On the other hand, if debottlenecking can be accomplished in increasing amounts at increasing costs, then the marginal 

cost curve will look smoother. 

Our point is that in one very common case -- smooth demand and cost curves -- the 

standard critical loss analysis is inconsistent with economic theory, unless firms engage in premerger coordination. Our view is that the use of standard critical loss analysis must be 

accompanied with a credible explanation for why special conditions exist that make the analysis 

consistent with economic theory. While it is possible that demand or cost curves are kinked at or 

near the prices that prevail just prior to a merger, an analyst using standard critical loss analysis 

must provide evidence demonstrating this if the analysis is to be given any weight. 

IV. Examples 

 Standard critical loss analysis has been applied in numerous antitrust cases before the 

Federal antitrust agencies and in Federal Court. In this section we briefly describe two 

applications that were conducted in cases that went to trial in U.S. District Court. In each case 

we show that the conclusions are likely to change when the analysis is made consistent with 

standard economic theory. 
25

A. Tenet Healthcare 

 In the Federal Trade Commission, et al. v. Tenet Healthcare Corporation, et al. (Tenet 

Healthcare), two owners of hospitals in the Poplar Bluff, MO area were attempting to merge. 

Tenet, the acquiring firm, owned one hospital in Poplar Bluff (Lucy Lee) and another hospital 

(Twin Rivers) within an hour’s driving time. Doctor’s Regional Medical Center (DRMC), the 

acquisition target, was a single hospital in Poplar Bluff. In addition, there were four small 

regional hospitals within an hour’s driving time. The merging hospitals provided both primary 

and secondary care. The smaller hospitals provided only primary care. The FTC claimed that 

the relevant geographic market included these seven hospitals. The defendant argued that the 

relevant market included several other hospitals more than a one hour drive from Poplar Bluff, 

including one very large hospital (over 1000 beds) that was more than three and a half hours 

driving time from Poplar Bluff.24

The defendant’s expert report made the argument that because the merging hospitals had 

very large margins, the percentage of patients they would have to lose to other hospitals to make 

a price increase unprofitable was not very large. In particular, the report showed that one of the 

merging hospitals, Lucy Lee, had a margin of 65.9 percent and thus would lose money by 

increasing price by 5 percent if at least 7.1 percent of its patients switched to another hospital. 

Based on survey evidence that the expert interpreted as showing that many more than 7.1 percent 

of patients would switch, the report argued that the existence of high margins made it very 

unlikely that the merger would result in a price increase. There was nothing in the record to 

indicate that the expert had presented evidence that the firms were colluding prior to the merger, 

 

24 This information is taken from FTC and State of Missouri v. Tenet Healthcare et al., Preliminary Injunction 

Decision, U.S. District Court, Eastern District of Missouri, Eastern Division, Filed July 30, 1998, p. 3,4,10, and 

Expert Report of Barry Harris, Exhibit 5. Driving time was computed using MapQuest. 

 
26

or that demand or cost curves were kinked at or just above the pre-merger price. 

 If one uses the information that the margins provide about the willingness of customes to 

switch, however, the story is likely quite different. Conditions (12) and (13) imply that a 5 

percent price increase by both hospitals after the merger would be unprofitable if and only if 

 Cross = > E

+ .107 .659(.05 .659)

.05

or 

 .05 .071

.05 .659

= > Diversion Ratio

+ . 

That is, a five percent price increase by both hospitals would have been profitable unless the 

hospitals were not very close substitutes, with a cross elasticity less than .107 and a diversion 

ratio less than 7.1 percent. This implies that more than 92 percent of the patients at either Lucy 

Lee or DRMC would have as their second choice some hospital outside of Poplar Bluff instead 

of the other hospital in Poplar Bluff. This seems unlikely, given that Lucy Lee and DRMC were 

less than 3 miles apart, while competing hospitals providing both primary and secondary care 

were over 50 miles away.25 Thus, it is not surprising that other evidence in the record indicated 

that the two hospitals in Poplar Bluff were highly competitive. For example, third party payers 

attributed their success in obtaining discounted rates to “the fierce competition” between the two 

hospitals.26 

 As is often the case in standard critical loss analysis, the large margins asserted by the 

defendant’s expert were not consistent with testimony about the willingness of customers to 

switch. In this case, a telephone survey presented by the experts purported to show that many 

 

25 The other Tenet hospital, Twin Rivers, was less than 50 miles away and did provide both primary and secondary 

care. 
27

patients would switch to other hospitals if faced with a 5 percent price increase. How can this 

inconsistency be explained or resolved? If we assume that the testimony about the how readily 

customers would switch products was valid (in this case, the telephone survey), one of five 

things would have to be true. First, the merging parties might have been over-pricing their 

product. That is, they might have been able to increase their profits, without a merger, simply by 

lowering their prices and gaining a large number of new customers. Obviously, since the 

merging parties provided the testimony about customer substitution, they would have this 

information after the merger. If they were over-pricing their product at the time of the merger, 

then one would have expected prices to drop if the merger were blocked. A second possibility is 

that the pre-merger prices were above the unilateral profit maximizing level because of collusion 

(explicit or tacit). Since collusion rarely works perfectly forever, one would have expected it to 

break down at some point if the merger had been blocked, causing prices to drop. With the 

merger, however, collusion would be easier to enforce, making this price drop less likely. A 

third possibility is that the defendant’s expert mis-measured the margin, i.e., that it was not as 

high as the expert claimed. This would obviously invalidate the conclusions of the critical loss 

analysis irrespective of whether they were consistent with standard economic theory. The fourth 

and fifth possibilities are that the hospital’s demand or cost curves were kinked at or near the 

prevailing price. As mentioned earlier, the expert did not provide evidence of such a kink. 

 Of course, a distinct possibility is that the testimony about the actual loss from a price 

increase was not valid. After all, if the parties thought this evidence was reasonable, they would 

have used it in pricing their products. In fact, when the court examined the telephone survey that 

formed the basis for the expert’s critical loss analysis, it found that its conclusion that a large 

number of patients would switch hospitals in response to a 5 percent price increase was invalid. 

 26 Preliminary Injunction Decision, op. cit., p. 6. 
28

By presenting this example we do not intend to suggest that there is no role for testimony 

about the responsiveness of demand to changes in price. Our point is that such testimony must 

be reconciled with other evidence, such as that embodied in the firms’ margins. Standard critical 

loss analysis fails to do this. 

B. Swedish Match 

 In Federal Trade Commission v. Swedish Match North America Inc., et al., two 

producers of loose leaf chewing tobacco were attempting to merge. Experts for the merging 

firms argued that margins in this industry were quite high, ranging from 55 to 68 percent. As in 

Tenet Healthcare, the defendant’s expert report made the argument that because margins were so 

high, a significant price increase by a hypothetical monopolist or by the merging firms after the 

merger was very unlikely. Also like the previous case, the expert report noted that the existence 

of high margins meant that the amount of sales that would have to be lost to make a five (or ten) 

percent price increase unprofitable was not very large. The report did not consider the fact that 

high margins also indicate that the amount of sales lost from a given price increase is likely to be 

quite small. In fact, in determining the critical loss, the report claimed to be conservative by 

using the smaller (55 percent) figure for the margin. While this does generate a smaller figure 

for the critical loss in sales necessary to make a given price increase unprofitable, it also makes it 

less likely that the actual loss in sales will exceed the critical loss, as we showed above. Thus, 

using the smaller margin figure is not conservative. 

 After determining the critical loss for a 5 percent price increase to be 8.3 percent 

(=.05/(.05+.55)), the defendants’ expert report then compared this to the actual loss implied by 
29

its estimate of the market elasticity of demand for loose leaf chewing tobacco.27 The market 

demand that was estimated was a smooth curve with no kinks. The market elasticity was 

estimated to be 2.3, which implied an actual loss from a 5 percent price increase of 10.6 

percent.28 Since the estimated actual loss of 10.6 percent exceeded the critical loss of 8.3 

percent, the report claimed to have shown that a 5 percent price increase by a hypothetical 

monopolist of loose leaf chewing tobacco would be unprofitable. The expert’s conclusion was 

that the relevant product market should include moist snuff in addition to loose leaf chewing 

tobacco. 

The expert’s calculation, based on standard critical loss analysis, is mathematically 

correct. However, the estimated market elasticity is inconsistent with margins as high as the 

expert claimed. With margins of 55 percent, the elasticity of demand for a single brand would be 

1.82 (1/.55=1.82) if prices were chosen unilaterally prior to the merger. If the margin were 

higher, the elasticity would have to be even smaller. Since the elasticity of demand for the whole 

market must be less than the elasticity of demand for a single brand, the claimed market demand 

elasticity of 2.3 is inconsistent with profit maximization.29

 Again, this example is not meant to disparage the use of demand estimation for defining 

markets and/or assessing market power in antitrust investigations. Our point is that econometric 

estimates of demand elasticities must be consistent with other evidence about substitution, such 

as that implied by margins. One cannot simultaneously claim that demand is very elastic for the 

 

27 The experts actually couched their analysis in terms of the critical elasticity above which a price increase would 

not be profitable. This analysis is mathematically equivalent to examining the critical loss above which a price 

increase would not be profitable. 

28 The estimated elasticity of 2.3 is a point elasticity, not an arc elasticity. Under constant elasticity demand 

(assumed by the expert), this implies that a five percent price increase will cause a 10.6 percent loss in sales. One 

can use the formulas in footnote 23 to verify this. 

29 The court did not rely on the econometric analysis of the parties in reaching its conclusion in this case. 
30

purposes of estimating lost sales from a price increase and that margins are very high, requiring 

that demand must be very inelastic. 

We explained above that in addition to margins, the cross elasticities of demand among 

the merging firms’ brands are critical for evaluating the profitability of a post-merger price 

increase. The defendant’s expert report in Swedish Match did not provide estimates of the crosselasticities among loose-leaf brands. However, it did present an estimate of the cross-elasticity 

of demand for all loose leaf chewing tobacco with respect to a price index for all moist snuff. 

This cross elasticity was estimated to be .5. Given this much substitution between two different

types of smokeless tobacco --- loose leaf chewing tobacco and moist snuff --- it seems likely that 

the amount of substitution between the two leading brands of loose leaf chewing tobacco would 

also be significant. By using equation (12), however, one can see that the cross-elasticity 

between the two brands would have to be much smaller than the cross elasticity between looseleaf and moist snuff to make a post-merger price increase of 5 percent unprofitable: 

Cross = > E

+ .152 .55(.05 .55)

.05 . 

So, unless the cross elasticity between two different types of smokeless tobacco is more than 

three times greater than the cross elasticity between the two leading brands of one type of 

smokeless tobacco (loose-leaf), the defendant’s own econometric analysis suggested that the 

merging firms would have found a 5 percent price increase to be profitable post-merger. 

V. Conclusion 

We have shown that the inference typically drawn from critical loss analysis --- that high 

margins make a merger less likely to be anticompetitive --- is often inconsistent with economic 

theory. Firms set their margins to maximize their profits. The more close substitutes there are 
31

for a firm’s product, the lower the firm’s margin must be to prevent customers from switching to 

those products. Conversely, the fewer the number of close substitutes a firm faces, the higher the 

margin will be. Thus, when two or more substitutes come under common ownership, the degree 

to which competition is reduced (loosely speaking) is greater when margins are high (because 

there is less competition to begin with) than when margins are low. Therefore, it should not be 

surprising that economic theory predicts that mergers tend to lead to greater, not smaller, price 

increases when margins are high rather than when margins are low. Conversely, theory predicts 

that mergers in more competitive markets (those with lower margins) are less likely to cause 

significant price increases than mergers in less competitive markets (those with higher margins), 

contrary to what critical loss analysis purports to show. In summary, it is the approach of the 

Merger Guidelines (mergers in concentrated markets are more likely to be anticompetitive) that 

is consistent with economic theory, not critical loss analysis as it is typically practiced. 

 Where does this leave critical loss analysis as tool in antitrust practice? In our opinion, 

critical loss analysis has led to enormous confusion about the economic factors that govern firms' 

pricing incentives. The technique has been mis-used so frequently that arguments that are 

inconsistent with basic economic theory have almost gained a measure of legitimacy in antitrust 

cases. It is now common for people to assume that high pre-merger margins imply broader 

markets and/or a smaller likelihood of anticompetitive effects. This article has shown that this 

assumption is not correct because it is generally not consistent with basic economic theory.