opinion: UNITED STATES v. GENERAL DYNAMICS CORP. et al.
  No. 72-402.
  Argued December 5, 1973
  Decided March 19, 1974
  Stewart, J., delivered the opinion of the Court, in which Burger, C. J., and Blackmun, Powell, and Rehnquist, JJ., joined. Douglas, J., filed a dissenting opinion in which Brennan, White, and Marshall, JJ., joined, post, p. 511.
  Deputy Solicitor General Friedman argued the cause for the United States. With him on the briefs were Solicitor General Bork, former Solicitor General Griswold, Assistant Attorney General Kauper, Mark L. Evans, and Carl D. Lawson.
  Reuben L. Hedlund argued the cause for appellees. With him on the brief were Hammond E. Chaff etz, Donald G. Kempf, Jr., and Albert E. Jenner, Jr.
  MR. Justice Stewart
  delivered the opinion of the Court.
  On September 22, 1967, the Government commenced this suit in the United States District Court for the Northern District of Illinois, challenging as violative of § 7 of the Clayton Act, 38 Stat. 731, as amended, 15 U. S. C. § 18, the acquisition of the stock of United Electric Coal Companies by Material Service Corp. and its successor, General Dynamics Corp. After lengthy discovery proceedings, a trial was held from March 30 to April 22, 1970, and on April 13, 1972, the District Court issued an opinion and judgment finding no violation of the Clayton Act. 341 F. Supp. 534. The Government appealed directly to this Court pursuant to the Expediting Act, 15 U. S. C. § 29, and we noted probable jurisdiction. 409 U. S. 1058.
  I
  At the time of the acquisition involved here, Material Service Corp. was a large midwest producer and supplier of building materials, concrete, limestone, and coal. All of its coal production was from deep-shaft mines operated by it or its affiliate, appellee Freeman Coal Mining Corp., and production from these operations amounted to 6.9 million tons of coal in 1959 and 8.4 million tons in 1967. In 1954, Material Service began to acquire the stock of United Electric Coal Companies. United Electric at all relevant times operated only strip or open-pit mines in Illinois and Kentucky; at the time of trial in 1970 a number of its mines had closed and its operations had been reduced to four mines in Illinois and none in Kentucky. In 1959, it produced 3.6 million tons of coal, and by 1967, it had increased this output to 5.7 million tons. Material Service’s purchase of United Electric stock continued until 1959. At this point Material’s holdings amounted to more than 34% of United Electric’s outstanding shares and — all parties are now agreed on this point — Material had effective control of United Electric. The president of Freeman was elected chairman of United Electric’s executive committee, and other changes in the corporate structure of United Electric were made at the behest of Material Service.
  Some months after this takeover, Material Service was itself acquired by the appellee General Dynamics Corp. General Dynamics is a large diversified corporation, much of its revenues coming from sales of aircraft, communications, and marine products to Government agencies. The trial court found that its purchase of Material Service was part of a broad diversification program aimed at expanding General Dynamics into commercial, nondefense business. As a result of the purchase of Material Service, and through it, of Freeman and United Electric, General Dynamics became the Nation’s fifth largest commercial coal producer. During the early 1960’s General Dynamics increased its equity in United Electric by direct purchases of United Electric stock, and by 1966 it held or controlled 66.16% of United Electric's outstanding shares. In September 1966 the board of directors of General Dynamics authorized a tender offer to holders of the remaining United Electric stock. This offer was successful, and United Electric shortly thereafter became a wholly owned subsidiary of General Dynamics.
  The thrust of the Government's complaint was that the acquisition of United Electric by Material Service in 1969 violated § 7 of the Clayton Act because the takeover substantially lessened competition in the production and sale of coal in either or both of two geographic markets. It contended that a relevant “section of the country” within the meaning of § 7 was, alternatively, the State of Illinois or the Eastern Interior Coal Province Sales Area, the latter being one of four major coal distribution areas recognized by the coal industry and comprising Illinois and Indiana, and parts of Kentucky, Tennessee, Iowa, Minnesota, Wisconsin, and Missouri.
  At trial controversy focused on three basic issues: the propriety of coal as a “line of commerce,” the definition of Illinois or the Eastern Interior Coal Province Sales Area as a relevant “section of the country,” and the probability of a lessening of competition within these or any other product and geographic markets resulting from the acquisition. The District Court decided against the Government on each of these issues.
  As to the relevant product market, the court found that coal faced strong and direct competition from other sources of energy such as oil, natural gas, nuclear energy, and geothermal power which created a cross-elasticity of demand among those various fuels. As a result, it concluded that coal, by itself, was not a permissible product market and that the “energy market” was the sole “line of commerce” in which anticompetitive effects could properly be canvassed.
  Similarly, the District Court rejected the Government’s proposed geographic markets on the ground that they were “based essentially on past and present production statistics and do not relate to actual coal consumption patterns.” 341 F. Supp., at 556. The court found that a realistic geographic market should be defined in terms of transportation arteries and freight charges that determined the cost of delivered coal to purchasers and thus the competitive position of various coal producers. In particular, it found that freight rate districts, designated by the Interstate Commerce Commission for determining rail transportation rates, of which there were four in the area served by the appel-lee companies, were the prime determinants for the geographic competitive patterns among coal producers. In addition, the court concluded that two large and specialized coal consumption units were sufficiently differentiable in their coal use patterns to be included as relevant geographic areas. In lieu of the State of Illinois or the Eastern Interior Coal Province Sales Area, the court accordingly found the relevant geographic market to be 10 smaller areas, comprising the two unique consumers together with four utility sales areas and four nonutility sales areas based on the ICC freight rate districts.
  Finally, and for purposes of this appeal most significantly, the District Court found that the evidence did not support the Government’s contention that the 1959 acquisition of United Electric substantially lessened competition in any product or geographic market. This conclusion was based on four determinations made in the court’s opinion, id., at 558-559. First, the court noted that while the number of coal producers in the Eastern Interior Coal Province declined from 144 to 39 during the period of 1957-1967, this reduction “occurred not because small producers have been acquired by others, but as the inevitable result of the change in the nature of demand for coal.” Consequently, the court found, “this litigation presents a very different situation from that in such cases as United States v. Philadelphia National Bank, 374 U. S. 321 (1963), and United States v. Von’s Grocery Co., 384 U. S. 270 (1966), where the Supreme Court was concerned with ‘preventing even slight increases in concentration.’ 374 U. S., at 365, n. 2.” 341 F. Supp., at 558. Second, the court noted that United Electric and Freeman were “predominantly complementary in nature” since “United Electric is a strip mining company with no experience in deep mining nor likelihood of acquiring it [and] Freeman is a deep mining company with no experience or expertise in strip mining.” Ibid. Third, the court found that if Commonwealth Edison, a large investor-owned public utility, were excluded, “none of the sales by United Electric in the period 1965 to 1967, the years chosen by the Government for analysis, would have or could have been competitive with Freeman, had the two companies been independent,” because of relative distances from potential consumers and the resultant impact on relative competitive position. Ibid. Finally, the court found that United Electric’s coal reserves were so low that its potential to compete with other coal producers in the future was far weaker than the aggregate production statistics relied on by the Government might otherwise have indicated. In particular, the court found that virtually all of United Electric’s proved coal reserves were either depleted or already committed by long-term contracts with large customers, and that United Electric’s power to affect the price of coal was thus severely limited and steadily diminishing. On the basis of these considerations, the court concluded: “Under these circumstances, continuation of the affiliation between United Electric and Freeman is not adverse to competition, nor would divestiture benefit competition even were this court to accept the Government's unrealistic product and geographic market definitions.” Id., at 560.
  II
  The Government sought to prove a violation of § 7 of the Clayton Act principally through statistics showing that within certain geographic markets the coal industry was concentrated among a small number of large producers; that this concentration was increasing; and that the acquisition of United Electric would materially enlarge the market share of the acquiring company and thereby contribute to the trend toward concentration.
  The concentration of the coal market in Illinois and, alternatively, in the Eastern Interior Coal Province was demonstrated by a table of the shares of the largest two, four, and 10 coal-producing firms in each of these areas for both 1957 and 1967 that revealed the following:
  Eastern Interior
  Coal Province Illinois
  1957 1967 1957 1967
  Top 2 firms. 29.6 4813 37B 52^9
  Top 4 firms. 43.0 62.9 54.5 75.2
  Top 10 firms. 65.5 91.4 84.0 98.0
  These statistics, the Government argued, showed not only that the coal industry was concentrated among a small number of leading producers, but that the trend had been toward increasing concentration. Furthermore, the undisputed fact that the number of coal-producing firms in Illinois decreased almost 73% during the period of 1957 to 1967 from 144 to 39 was claimed to be indicative of the same trend. The acquisition of United Electric by Material Service resulted in increased concentration of coal sales among the leading producers in the areas chosen by the Government, as shown by the following table:
  1959
  1967
  Share of top 2 but for merger
  Share of top 2 given merger
  Percent increase
  Share of top 2 but for merger
  Share of top 2 given merger
  Percent increase
  Province . 33.1 37.9 14.5 45.0 48.6 8.0
  Illinois . 36.6 44.3 22.4 44.0 52.9 20.2
  Finally, the Government's statistics indicated that the acquisition increased the share of the merged company in the Illinois and Eastern Interior Coal Province coal markets by significant degrees:
  Province Illinois
  Share Share
  Rank (percent) Rank (percent)
  1959
  Freeman . 2 7.6 2 15.1
  United Electric. 6 4.8 5 8.1
  Combined . 2 12.4 1 23.2
  1967
  Freeman . 5 6.5 2 12.9
  United Electric. 9 4.4 6 8.9
  Combined . 2 10.9 2 21.8
  In prior decisions involving horizontal mergers between competitors, this Court has found prima facie violations of § 7 of the Clayton Act from aggregate statistics of the sort relied on by the United States in this case. In Brown Shoe Co. v. United States, 370 U. S. 294, the Court reviewed the legislative history of the most recent amendments to the Act and found that “[t]he dominant theme pervading congressional consideration of the 1950 amendments was a fear of what was considered to be a rising tide of economic concentration in the American economy.” Id., at 315. A year later, in United States v. Philadelphia National Bank, 374 U. S. 321, the Court clarified the relevance of a statistical demonstration of concentration in a particular industry and of the effects thereupon of a merger or acquisition with the following language:
  “This intense congressional concern with the trend toward concentration warrants dispensing, in certain cases, with elaborate proof of market structure, market behavior, or probable anticompetitive effects. Specifically, we think that a merger which produces a firm controlling an undue percentage share of the relevant market, and results in a significant increase in the concentration of firms in that market, is so inherently likely to lessen competition substantially that it must be enjoined in the absence of evidence clearly showing that the merger is not likely to have such anticompetitive effects.” Id., at 363.
  See also United States v. Continental Can Co., 378 U. S. 441, 458; United States v. Von’s Grocery Co., 384 U. S., at 277; United States v. Pabst Brewing Co., 384 U. S. 546, 550-552.
  The effect of adopting this approach to a determination of a “substantial” lessening of competition is to allow the Government to rest its case on a showing of even small increases of market share or market concentration in those industries or markets where concentration is already great or has been recently increasing, since “if concentration is already great, the importance of preventing even slight increases in concentration and so preserving the possibility of eventual deconcentration is correspondingly great.” United States v. Aluminum Co. of America, 377 U. S. 271, 279, citing United States v. Philadelphia National Bank, supra, at 365 n. 42.
  While the statistical showing proffered by the Government in this case, the accuracy of which was not discredited by the District Court or contested by the appellees, would under this approach have sufficed to support a finding of “undue concentration” in the absence of other considerations, the question before us is whether the District Court was justified in finding that other pertinent factors affecting the coal industry and the business of the appellees mandated a conclusion that no substantial lessening of competition occurred or was threatened by the acquisition of United Electric. We are satisfied that the court’s ultimate finding was not in error.
  In Brown Shoe v. United States, supra, we cautioned that statistics concerning market share and concentration, while of great significance, were not conclusive indicators of anticompetitive effects:
  “Congress indicated plainly that a merger had to be functionally viewed, in the context of its particular industry.” 370 U. S., at 321-322.
  “Statistics reflecting the shares of the market controlled by the industry leaders and the parties to the merger are, of course, the primary index of market power; but only a further examination of the particular market — its structure, history and probable future — can provide the appropriate setting for judging the probable anticompetitive effect of the merger.” Id., at 322 n. 38.
  See also United States v. Continental Can Co., supra, at 458. In this case, the District Court assessed the evidence of the “structure, history and probable future” of the coal industry, and on the basis of this assessment found no substantial probability of anticompetitive effects from the merger.
  Much of the District Court’s opinion was devoted to a description of the changes that have affected the coal industry since World War II. On the basis of more than three weeks of testimony and a voluminous record, the court discerned a number of clear and significant developments in the industry. First, it found that coal had become increasingly less able to compete with other sources of energy in many segments of the energy market. Following the War the industry entirely lost its largest single purchaser of coal — the railroads — and faced increasingly stiffer competition from oil and natural gas as sources of energy for industrial and residential uses. Because of these changes in consumption patterns, coal's share of the energy resources consumed in this country fell from 78.4% in 1920 to 21.4% in 1968. The court reviewed evidence attributing this decline not only to the changing relative economies of alternative fuels and to new distribution and consumption patterns, but also to more recent concern with the effect of coal use on the environment and consequent regulation of the extent and means of such coal consumption.
  Second, the court found that to a growing extent since 1954, the electric utility industry has become the mainstay of coal consumption. While electric utilities consumed only 15.76% of the coal produced nationally in 1947, their share of total consumption increased every year thereafter, and in 1968 amounted to more than 59% of all the coal consumed throughout the Nation.
  Third, and most significantly, the court found that to an increasing degree, nearly all coal sold to utilities is transferred under long-term requirements contracts, under which coal producers promise to meet utilities’ coal consumption requirements for a fixed period of time, and at predetermined prices. The court described the mutual benefits accruing to both producers and consumers of coal from such long-term contracts in the following terms:
  “This major investment [in electric utility equipment] can be jeopardized by a disruption in the supply of coal. Utilities are, therefore, concerned with assuring the supply of coal to such a plant over its life. In addition, utilities desire to establish in advance, as closely as possible, what fuel costs will be for the life of the plant. For these reasons, utilities typically arrange long-term contracts for all or at least a major portion of the total fuel requirements for the life of the plant. . . .
  “The long-term contractual commitments are not only required from the consumer’s standpoint, but are also necessary from the viewpoint of the coal supplier. Such commitments may require the development of new mining capacity. . . . Coal producers have been reluctant to invest in new mining capacity in the absence of long-term contractual commitments for the major portion of the mine’s capacity. Furthermore, such long-term contractual commitments are often required before financing for the development of new capacity can be obtained by the producer.” 341 F. Supp., at 543 (footnote omitted).
  These developments in the patterns of coal distribution and consumption, the District Court found, have limited the amounts of coal immediately available for “spot” purchases on the open market, since “[t]he growing practice by coal producers of expanding mine capacity only to meet long-term contractual commitments and the gradual disappearance of the small truck mines has tended to limit the production capacity available for spot sales.” Ibid.
  Because of these fundamental changes in the structure of the market for coal, the District Court was justified in viewing the statistics relied on by the Government as insufficient to sustain its case. Evidence of past production does not, as a matter of logic, necessarily give a proper picture of a company's future ability to compete. In most situations, of course, the unstated assumption is that a company that has maintained a certain share of a market in the recent past will be in a position to do so in the immediate future. Thus, companies that have controlled sufficiently large shares of a concentrated market are barred from merger by § 7, not because of their past acts, but because their past performances imply an ability to continue to dominate with at least equal vigor. In markets involving groceries or beer, as in Von’s Grocery, supra, and Pabst, supra, statistics involving annual sales naturally indicate the power of each company to compete in the future. Evidence of the amount of annual sales is relevant as a prediction of future competitive strength, since in most markets distribution systems and brand recognition are such significant factors that one may reasonably suppose that a company which has attracted a given number of sales will retain that competitive strength.
  In the coal market, as analyzed by the District Court, however, statistical evidence of coal production was of considerably less significance. The bulk of the coal produced is delivered under long-term requirements contracts, and such sales thus do not represent the exercise of competitive power but rather the obligation to fulfill previously negotiated contracts at a previously fixed price. The focus of competition in a given time frame is not on the disposition of coal already produced but on the procurement of new long-term supply contracts. In this situation, a company's past ability to produce is of limited significance, since it is in a position to offer for sale neither its past production nor the bulk of the coal it is presently capable of producing, which is typically already committed under a long-term supply contract. A more significant indicator of a company’s power effectively to compete with other companies lies in the state of a company’s uncommitted reserves of recoverable coal. A company with relatively large supplies of coal which are not already under contract to a consumer will have a more important influence upon competition in the contemporaneous negotiation of supply contracts than a firm with small reserves, even though the latter may presently produce a greater tonnage of coal. In a market where the availability and price of coal are set by long-term contracts rather than immediate or short-term purchases and sales, reserves rather than past production are the best measure of a company’s ability to compete.
  The testimony and exhibits in the District Court revealed that United Electric’s coal reserve prospects were “unpromising.” 341 F. Supp., at 559. United’s relative position of strength in reserves was considerably weaker than its past and current ability to produce. While United ranked fifth among Illinois coal producers in terms of annual production, it was 10th in reserve holdings, and controlled less than 1% of the reserves held by coal producers in Illinois, Indiana, and western Kentucky. Id., at 538. Many of the reserves held by United had already been depleted at the time of trial, forcing the closing of some of United’s midwest mines. Even more significantly, the District Court found that of the 52,033,304 tons of currently mineable reserves in Illinois, Indiana, and Kentucky controlled by United, only four million tons had not already been committed under long-term contracts. United was found to be -facing the future with relatively depleted resources at its disposal, and with the vast majority of those resources already committed under contracts allowing no further adjustment in price. In addition, the District Court found that “United Electric has neither the possibility of acquiring more [reserves] nor the ability to develop deep coal reserves,” and thus was not in a position to increase its reserves to replace those already depleted or committed. Id., at 560.
  Viewed in terms of present and future reserve prospects — and thus in terms of probable future ability to compete — rather than in terms of past production, the District Court held that United Electric was a far less significant factor in the coal market than the Government contended or the production statistics seemed to indicate. While the company had been and remained a “highly profitable” and efficient producer of relatively large amounts of coal, its current and future power to compete for subsequent long-term contracts was severely limited by its scarce uncommitted resources. Irrespective of the company's size when viewed as a producer, its weakness as a competitor was properly analyzed by the District Court and fully substantiated that court’s conclusion that its acquisition by Material Service would not “substantially . . . lessen competition . . . .” The validity of this conclusion is not undermined, we think, by the three-faceted attack made upon it by the Government in this Court — to which we now turn.
  Ill
  First, the Government urges that the court committed legal error by giving undue consideration to facts occurring after the effective acquisition in 1959. In FTC v. Consolidated Foods Corp., 380 U. S. 592, 598, this Court stated that postacquisition evidence tending to diminish the probability or impact of anti-competitive effects might be considered in a § 7 case. See also United States v. E. I. du Pont de Nemours & Co., 353 U. S. 586, 597 et seq., 602 et seq. But in Consolidated Foods, supra, and in United States v. Continental Can Co., 378 U. S., at 463, the probative value of such evidence was found to be extremely limited, and judgments against the Government were in each instance reversed in part because “too much weight” had been given to postacquisition events. The need for such a limitation is obvious. If a demonstration that no anti-competitive effects had occurred at the time of trial or of judgment constituted a permissible defense to a § 7 divestiture suit, violators could stave off such actions merely by refraining from aggressive or anticompetitive behavior when such a suit was threatened or pending.
  Furthermore, the fact that no concrete anticompetitive symptoms have occurred does not itself imply that competition has not already been affected, “for once the two companies are united no one knows what the fate of the acquired company and its competitors would have been but for the merger.” FTC v. Consolidated Foods, supra, at 598. And, most significantly, § 7 deals in “probabilities, not certainties,” Brown Shoe v. United States, 370 U. S., at 323, and the mere nonoccurrence of a substantial lessening of competition in the interval between acquisition and trial does not mean that no substantial lessening will develop thereafter; the essential question remains whether the probability of such future impact exists at the time of trial.
  In this case, the District Court relied on evidence relating to changes in the patterns and structure of the coal industry and in United Electric’s coal reserve situation after the time of acquisition in 1959. Such evidence could not reflect a positive decision on the part of the merged companies to deliberately but temporarily refrain from anticompetitive actions, nor could it reasonably be thought to reflect less active competition than that which might have occurred had there not been an acquisition in 1959. As the District Court convincingly found, the trend toward increased dependence on utilities as consumers of coal and toward the near-exclusive use of long-term contracts was the product of inevitable pressures on the coal industry in all parts of the country. And, unlike evidence showing only that no lessening of competition has yet occurred, the demonstration of weak coal resources necessarily and logically implied that United Electric was not merely disinclined but unable to compete effectively for future contracts. Such evidence went directly to the question of whether future lessening of competition was probable, and the District Court was fully justified in using it.
  Second, the Government contends that reliance on depleted and committed resources is essentially a “failing company” defense which must meet the strict limits placed on that defense by this Court’s decisions in United States v. Third National Bank in Nashville, 390 U. S. 171; Citizen Publishing Co. v. United States, 394 U. S. 131; and United States v. Greater Buffalo Press, 402 U. S. 549. The failing-company doctrine, recognized as a valid defense to a § 7 suit in Brown Shoe, supra, at 346, was first announced by this Court in International Shoe Co. v. FTC, 280 U. S. 291, and was preserved by explicit references in the legislative history of the modern amendments to § 7. H. R. Rep. No. 1191, 81st Cong., 1st Sess., 6 (1949); S. Rep. No. 1775, 81st Cong., 2d Sess., 7 (1950). A company invoking the defense has the burden of showing that its “resources [were] so depleted and the prospect of rehabilitation so remote that it faced the grave probability of a business failure . . . ,” International Shoe, supra, at 302, and further that it tried and failed to merge with a company other than the acquiring one, Citizen Publishing Co., supra, at 138; Greater Buffalo Press, supra, at 555.
  The Government asserts that United Electric was a healthy and thriving company at the time of the acquisition and could not be considered on the brink of failure, and also that the appellees have not shown that Material Service was the only available acquiring company. . These considerations would be significant if the District Court had found no violation of § 7 by reason of United Electric's being a failing company, but the District Court's conclusion was not, as the Government suggests, identical with or even analogous to such a finding. The failing-company defense presupposes that the effect on competition and the “loss to [the company’s] stockholders and injury to the communities where its plants were operated,” International Shoe, supra, at 302, will be less if a company continues to exist even as a party to a merger than if it disappears entirely from the market. It is, in a sense, a “lesser of two evils” approach, in which the possible threat to competition resulting from an acquisition is deemed preferable to the adverse impact on competition and other losses if the company goes out of business. The appellees’ demonstration of United’s weak reserves position, however, proved an entirely different point. Rather than showing that United would have gone out of business but for the merger with Material Service, the finding of inadequate reserves went to the heart of the Government’s statistical prima facie case based on production figures and substantiated the District Court’s conclusion that United Electric, even if it remained in the market, did not have sufficient reserves to compete effectively for long-term contracts. The failing-company defense is simply inapposite to this finding and the failure of the appellees to meet the prerequisites of that doctrine did not detract from the validity of the court’s analysis.
  Finally, the Government contends that the factual underpinning of the District Court’s opinion was not supported by the evidence contained in the record, and should be re-evaluated by this Court. The findings and conclusions of the District Court are, of course, governed by the “clearly erroneous” standard of Fed. Rule Civ. Proc. 52 (a) just as fully on direct appeal to this Court as when a civil case is being reviewed by a court of appeals. The record in this case contains thousands of pages of transcript and hundreds of exhibits. Little purpose would be served by discussing in detail each of the Government’s specific factual contentions. Suffice it to say that we find the controlling findings and conclusions contained in the District Court’s careful and lengthy opinion to be supported by the evidence in the record and not clearly erroneous.
  One factual claim by the Government, however, goes to the heart of the reasoning of the District Court and thus is worthy of explicit note here. The Government asserts that the paucity of United Electric's coal reserves could not have the significance perceived by the District Court, since all companies engaged in extracting minerals at some point deplete their reserves and then acquire new reserves or the new technology required to extract more minerals from their existing holdings. United Electric, the Government suggests, could at any point either purchase new strip reserves or acquire the expertise to ‘recover currently held deep reserves.
  But the District Court specifically found new strip reserves not to be available: “Evidence was presented at trial by experts, by state officials, by industry witnesses and by the Government itself indicating that economically mineable strip reserves that would permit United Electric to continue operations beyond the life of its present mines are not available. The Government failed to come forward with any evidence that such reserves are ;presently available.” 341 F. Supp., at 559. In addition, there was considerable testimony at trial, apparently credited by the District Court, indicating that United Electric and others had tried to find additional strip reserves not already held for coal production, and had been largely unable to do so.
  Moreover, the hypothetical possibility that United Electric might in the future acquire the expertise to mine deep reserves proves nothing — or too much. As the Government pointed out in its brief and at. oral argument, in recent years a number of companies with no prior experience in extracting coal have purchased coal reserves and entered the coal production business in order to diversify and complement their current operations. The mere possibility that United Electric, in common with all other companies with the inclination and the corporate treasury to do so, could some day expand into an essentially new line of business does not depreciate the validity of the conclusion that United Electric at the time of the trial did not have the power to compete on a significant scale for the procurement of future long-term contracts, nor does it vest in the production statistics relied on by the Government more significance than ascribed to them by the District Court.
  IV
  In addition to contending that the District Court erred in finding that the acquisition of United Electric would not substantially lessen competition, the Government urges us to review the court’s determinations of the proper product and geographic markets. The Government suggests that while the “energy market” might have been an appropriate “line of commerce,” coal also had sufficient “practical indicia” as a separate “line of commerce” to qualify as an independent and consistent submarket. Cf. United States v. Continental Can Co., 378 U. S., at 456-457. It also suggests that irrespective of the validity of the criteria adopted by the District Court in selecting its 10 geographic markets, competition between United Electric and Material Service within the larger alternative geographic markets claimed by the Government established those areas as a permissible “section of the country” within the meaning of § 7.
  While under normal circumstances a delineation of proper geographic and product markets is a necessary precondition to assessment of the probabilities of a substantial effect on competition within them, in this case we nevertheless affirm the District Court’s judgment without reaching these questions. By determining that the amount and availability of usable reserves, and not the past annual production figures relied on by the Government, were the proper indicators of future ability to compete, the District Court wholly rejected the Government’s prima facie case. Irrespective of the markets within which the acquiring and the acquired company might be viewed as competitors for purposes of this § 7 suit, the Government’s statistical presentation simply did not establish that a substantial lessening of competition was likely to occur in any market. By concluding that “divestiture [would not] benefit competition even were this court to accept the Government’s unrealistic product and geographic market definitions,” 341 F. Supp., at 560, the District Court rendered superfluous its further determinations that the Government also erred in its choice of relevant markets. Since we agree with the District Court that the Government’s reliance on production statistics in the context of this case was insufficient, it follows that the judgment before us may be affirmed without reaching the issues of geographic and product markets.
  The judgment of the District Court is affirmed.
  It is so ordered.
  United Electric also had coal-mining operations in Utah and other Western States. The Government has not contended, however, that these holdings are. of any releyance in this case.
  Section 7 of the Clayton Act reads in pertinent part as follows:
  “No corporation engaged in commerce shall acquire, directly or indirectly, the whole or any part of the stock or other share capital and no corporation subject to the jurisdiction of the Federal Trade Commission shall acquire the whole or any part of the assets of another corporation engaged also in commerce, where in anjr line of commerce in any section of the country, the effect of such acquisition may be substantially to lessen competition, or to tend to create a monopoly.”
  Testimony at trial indicated that the Eastern Interior Coal Province — the area of coal production upon which the Eastern Coal Province Sales Area was based — was originally named by United States Geological Survey maps of the coalfields in the United States and described one portion of a sequence of coal-bearing rock formations known geologically as the Pennsylvania System. The Sales Area of the Eastern Interior Coal Province was derived from the assumption, acknowledged in the trial court’s opinion, that the high costs of transporting coal — which may amount to 40% of the price of delivered coal — will inevitably give producers of coal a clear competitive advantage in sales in the immediate areas of the mines.
  The trial court found that Commonwealth Edison, a large private electric utility with generation facilities in many parts of Illinois, and the Metropolitan Chicago Interstate Air Quality Control Region constituted separate and unique geographic regions. Commonwealth Edison was found to have unique attributes because of the great size of its coal consumption requirements, its distinctive distribution patterns, and its extensive commitment to air pollution programs and the development of nuclear energy. The Chicago Control Region, a congressional designated area consisting of six counties in Illinois and two in Indiana, was distinguished from other geographic markets because of the impact of existing and anticipated air pollution regulations which would create special problems in the competition for coal sales contracts. 341 F. Supp. 534, 557.
  The figures for 1967 reflect the impact on market concentration of the acquisition involved here.
  The figures demonstrating the degree of concentration in the two coal markets chosen by the Government were roughly comparable to those in United States v. Von’s Grocery Co., 384 U. S. 270, where the top four firms in the market controlled 24.4% of the sales, the top eight 40.9%, and the top 12 48.8%. See id., at 281 (White, J., concurring). See also United States v. Pabst Brewing Co., 384 U. S. 546, 551, where the top four producers of beer in Wisconsin were found to control 47.74% of the market, and the top 10 in the Nation and the local three-state area to control 45.06% and 58.93%, respectively. The statistics in the present case appear to represent a less advanced state of concentration than those involved in United States v. Aluminum Co. of America, 377 U. S. 271, 279, where the two largest firms held 50% of the market, and the top five and the top nine controlled, respectively, 76% and 95.7%; and in United States v. Philadelphia National Bank, 374 U. S. 321, 365, where the two largest banks controlled 44% of the pre-merger market.
  The percentage increase in concentration asserted here was thus analogous to that found in Von’s Grocery, supra, where the concentration among the top four, eight, and 12 firms was increased, respectively, by 18.0%, 7.6%, and 2.5% as a result of the merger invalidated there. In Philadelphia Bank, supra, the 34% increase in concentration in the two largest firms from 44% to 59% was found to be clearly significant. 374 U. S., at 365.
  The 1959 Illinois figure of 23.2% was asserted by the Government to be comparable to the 23.94% share of the Wisconsin beer market found to be significant in Pabst, supra, and the 25% share controlled by the merged company in United States v. Continental Can Co., 378 U. S. 441, 461. The Province figure of 12.4% was compared with the shares held by the merged companies in Von’s Grocery (7.5%), and in the Pabst national (4.49%) and three-state (11.32%) markets.
  In 1968, electric utilities accounted for 59.09% of United States coal consumption, coke plants 18.20%, cement mills 1.88%, other manufacturing (including steel and rolling mills) 17.70%, and retail and miscellaneous consumers 3.14%.
  The District Court found that while United Electric held six mines operating in the midwest in 1948, it had opened only three new ones since then and four had closed because of exhaustion of reserves. The court found that the evidence showed that reserves in two other mines would soon be depleted, and the appellees inform us in their briefs that these events have already occurred.
  As an example of the impact of depleted or committed reserves on a company's ability to compete for long-term contracts, the District Court noted that a number of requirements contracts signed by United Electric to supply coal to electric utilities were backed up by reserves belonging to Freeman and “could not have been obtained without that guarantee” because of the utilities’ fear that the contract obligation could not otherwise be fulfilled. 341 F. Supp., at 559 (emphasis in original).
  The court’s reliance on such facts and the absence of specific findings of fact concerning the competitive situation in 1959, at which point both sides now agree the acquisition took place, may have been engendered by the Government’s apparent inconsistency in its position concerning the critical date. Certain of the ap-pellees’ proposed findings of fact concerning United Electric’s resources in 1959 and its attempts to increase its depleted holdings were termed "irrelevant” by the Government at the trial.
  The mere nonoccurrence of anticompetitive effects from a merger would, of course, merely postpone rather than preclude a divestiture suit. This Court indicated in United, States v. E. I. du Pont de Nemours & Co., 353 U. S. 586, 597, that a merger may be attacked ab initio long after its culmination if effect on competition not apparent immediately after the merger subsequently appears, since § 7 was designed to arrest the creation of monopolies “ 'in their incipiency’ ” and “ ‘incipiency’ . . . denotes not the time the stock was acquired, but any time when the acquisition threatens to ripen into a prohibited effect. . . .” See also FTC v. Consolidated Foods Corp., 380 U. S. 592, 598. The scope this “time of suit” concept gives to the Government in attacking mergers under § 7 is discussed in Orrick, The Clayton Act: Then and Now, 24 ABA Antitrust Section 44 (1964); Subcommittee on Section 7, The Backward Sweep Theory and the Oligopoly Problem, 32 ABA Antitrust L. J. 306 (1966). In the context of the present case, the “time of suit” rule coupled with the limited weight given to post-merger evidence of no anticompetitive impact tends to give the Government a “heads-I-win, tails-you-lose” advantage over a § 7 defendant: post-merger evidence showing a lessening of competition may constitute an “incipiency” on which to base a divestiture suit, but evidence showing that such lessening has not, in fact, occcurred cannot be accorded “too much weight.”
  In Citizen Publishing Co. v. United States, 394 U. S. 131, 138-139, “[t]he burden of proving that the conditions of the failing company doctrine have been satisfied” was found to be “on those who seek refuge under it.” (Footnote omitted.)
  Alternative rationales for the failing-company defense are discussed in Bok, Section 7 of the Clayton Act and the Merging of Law and Economics, 74 Harv. L. Rev. 226, 339-347 (1960); Comment, “Substantially to Lessen Competition . . Current Problems of Horizontal Mergers, 68 Yale L. J. 1627, 1662-1668 (1959).
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