CLARENCE THOMAS, Circuit Judge: Appellee Oy Tampella AB, a Finnish corporation, through its subsidiary Tamrock AG, manufactures and sells hardrock hydraulic underground drilling rigs (HHUDRs) in the United States and throughout the world. Appellee Baker Hughes Inc., a corporation based in Houston, Texas, owned a French subsidiary, Eimco Secoma, S.A. (Secoma), that was similarly involved in the HHUDR industry. In 1989, Tamrock proposed to acquire Seco-ma.
The United States challenged the proposed acquisition, charging that it would substantially lessen competition in the United States HHUDR market in violation of section 7 of the Clayton Act, 15 U.S.C. § 18.
1
In December 1989, the government sought and obtained a temporary restraining order blocking the transaction.
See
Temporary Restraining Order,
United States v. Baker Hughes Inc.,
No. 89-03333 (D.D.C. Dec. 15, 1989). In February 1990, the district court held a bench trial and issued a decision rejecting the government’s request for a permanent injunction and dismissing the section 7 claim.
See United States v. Baker Hughes Inc.,
The basic outline of a section 7 horizontal acquisition case is familiar. By showing that a transaction will lead to undue concentration in the market for a particular product in a particular geographic area,
2
the government establishes a presumption that the transaction will substantially lessen competition.
See United States v. Citizens & Southern Nat’l Bank,
By presenting statistics showing that combining the market shares of Tamrock and Secoma would significantly increase concentration in the already highly concentrated United States HHUDR market, the government established a prima facie case of anticompetitive effect. 3 The district court, however, found sufficient evidence that the merger would not substantially lessen competition to conclude that the'defendants had rebutted this prima facie case. The government did not produce any additional evidence showing a probability of substantially lessened competition, and thus failed to carry its ultimate burden of persuasion.
In this appeal, the government assails the court’s conclusion that the defendants rebutted the prima facie case. Doubtless aware that this court will set aside the district court’s findings of fact only if they are clearly erroneous, see Fed. R.Civ.P. 52(a), the government frames the issue as a pure question of law, which we review de novo. The government’s key contention is that the district court, which did not expressly state the legal standard that it applied in its analysis of rebuttal evidence, failed to apply a sufficiently stringent standard. The government argues that, as a matter of law, section 7 defendants can rebut a prima facie case only by a clear showing that entry into the market by competitors would be quick and effective. Because the district court failed to apply this standard, the government submits, the court erred in concluding that the proposed acquisition would not substantially lessen future competition in the United States HHUDR market.
We find no merit in the legal standard propounded by the government. It is devoid of support in the statute, in the case law, and in the government’s own Merger Guidelines. Moreover, it is flawed on its merits in three fundamental respects. First, it assumes that ease of entry by competitors is the only consideration relevant to a section 7 defendant’s rebuttal. Second, it requires that a defendant who seeks to show ease of entry bear the onerous burden of proving that entry will be “quick and effective.” Finally, by stating that the defendant can rebut a prima facie case only by a clear showing, the standard in effect shifts the government’s ultimate burden of persuasion to the defendant. Although the district court in this case did not expressly set forth a legal standard when it evaluated the defendants’ rebuttal, we have carefully reviewed the court’s thorough analysis of competitive conditions in the United States HHUDR market, and we are satisfied that the court effectively applied a standard faithful to section 7. 4 *984 Concluding that the court applied this legal standard to factual findings that are not clearly erroneous, we affirm the court’s denial of a permanent injunction and its dismissal of the government’s section 7 claim.
I.
It is a foundation of section 7 doctrine, disputed by no authority cited by the government, that evidence on a variety of factors can rebut a prima facie case. These factors include, but are not limited to, the absence of significant entry barriers in the relevant market. In this appeal, however, the government inexplicably imbues the entry factor with talismanic significance. If, to successfully rebut a prima facie case, a defendant must show that entry by competitors will be quick and effective, then other factors bearing on future competitiveness are all but irrelevant. The district court in this case considered at least two factors in addition to entry: the misleading nature of the statistics underlying the government’s prima facie case and the sophistication of HHUDR consumers. These non-entry factors provide compelling support for the court’s holding that Tam-rock’s acquisition of Secoma was not likely to lessen competition substantially. We have concluded that the court's consideration of these factors was crucial, and that the government’s fixation on ease of entry is misplaced.
Section 7 involves probabilities, not certainties or possibilities. 5 The Supreme Court has adopted a totality-of-the-circumstances approach to the statute, weighing a variety of factors to determine the effects of particular transactions on competition. That the government can establish a prima facie case through evidence on only one factor, market concentration, does not negate the breadth of this analysis. Evidence of market concentration simply provides a convenient starting point for a broader inquiry into future competitiveness; the Supreme Court has never indicated that a defendant seeking to rebut a prima facie case is restricted to producing evidence of ease of entry. Indeed, in numerous cases, defendants have relied entirely on non-entry factors in successfully rebutting a pri-ma facie case.
In
United States v. General Dynamics Corp.,
Indeed, the Court in
General Dynamics
emphasized the comprehensive nature of a section 7 inquiry, quoting at length from its decision a decade earlier in
Brown Shoe Co. v. United States,
be functionally viewed, in the context of its particular industry. That is, whether the consolidation was to take place in an industry that was fragmented rather than concentrated, that had seen a recent trend toward domination by a few leaders or had remained fairly consistent in its distribution of market shares among the participating companies, that had experienced easy access to markets by suppliers and easy access to suppliers by buyers or had witnessed foreclosure of business, that had witnessed the ready entry of new competition or the erection of barriers to prospective entrants, all were aspects, varying in importance with the merger under consideration, which would properly be taken into account.
In the wake of
General Dynamics,
the Supreme Court and lower courts have found section 7 defendants to have successfully rebutted the government’s prima fa-cie ease by presenting evidence on a variety of factors other than ease of entry.
See, e.g., Citizens & Southern,
Indeed, that a variety of factors other than ease of entry can rebut a prima facie ease has become hornbook law. See, e.g., P. Areeda & H. Hovenkamp, Antitrust Law ¶¶ 919’, 920.1, 921’, 925’, 934’, 935’, 939’, at 813-23 (Supp.1989) (other factors include significance of market shares and concentration, likelihood of express collusion or tacit coordination, and prospect of efficiencies from merger); H. Hovenkamp, Economics and Federal Antitrust Law § 11.6, at 307-11 (1985) (other factors include supply of irreplaceable raw materials, excess capacity, degree of product homogeneity, marketing and sales methods, and absence of a trend toward concentration); L. Sullivan, Handbook of the Law of Antitrust § 204, at 622-25 (1977) (other factors include industry structure, weakness of data underlying prima facie case, elasticity of industry demand, inter-industry cross-elasticities of demand and supply, product differentiation, and efficiency). See generally Antitrust Section, ABA, Horizontal Mergers: Law and Policy 162-75, 201-04, 219-63 (Monograph No. 12, 1986).
It is not surprising, then, that the Department of Justice’s own Merger Guidelines contain a detailed discussion of non-entry factors that can overcome a presumption of illegality established by market share statistics. See United States Dep’t of Justice, Merger Guidelines (June 14, 1984) [hereinafter Guidelines], reprinted in 4 Trade Reg.Rep. (CCH) ¶ 13,103, at 20,-561-64 (1988). According to the Guidelines, these factors include changing mar *986 ket conditions (§ 3.21), the financial condition of firms in the relevant market (§ 3.22), special factors affecting foreign firms (§ 3.23), the nature of the product and the terms of sale (§ 3.41), information about specific transactions and buyer market characteristics (§ 3.42), the conduct of firms in the market (§ 3.44), market performance (§ 3.45), and efficiencies (§ 3.5).
Given this acknowledged multiplicity of relevant factors, we are at a loss to understand on what basis the government has decided that “[t]o rebut the government’s prima facie case, the defendants were required to show that entry would be both quick and effective in preventing supra-competitive prices.” Brief for Appellants at 11-12 (emphasis added). If the district court in this case had focused exclusively on entry, it might be understandable that the government would mirror that focus in attacking the court’s conclusion. The district court, however, canvassed a number of non-entry factors that contributed to its conclusion that the defendants had rebutted the prima facie case. By ignoring these factors, the government’s arguments against that conclusion fall wide of the mark.
The district court’s analysis of this case is fully consonant with precedent and logic. The court reviewed the evidence proffered by the defendants as part of its overall assessment of future competitiveness in the United States HHUDR market. As noted above, the court gave particular weight to two non-entry factors: the flawed underpinnings of the government’s prima facie case and the sophistication of HHUDR consumers. The court’s consideration of these factors was not only appropriate, but imperative, because in this case these factors significantly affected the probability that the acquisition would have anticompetitive effects.
With respect to the first factor, the statistical basis of the prima facie case, the court accepted the defendants’ argument that the government’s statistics were misleading. Because the United States HHUDR market is minuscule, market share statistics are “volatile and shifting,”
The second non-entry factor that the district court considered was the sophistication of HHUDR consumers. HHUDRs currently cost hundreds of thousands of dollars, and orders can exceed $1 million. Id. at 8. These products are hardly trinkets sold to small consumers who may possess imperfect information and limited bargaining power. HHUDR buyers closely examine available options and typically insist on receiving multiple, confidential bids for each order. Id. This sophistication, the court found, was likely to promote competition even in a highly concentrated market. Id. at 11.
*987 The government has not provided us with any reason to suppose that these findings of fact are unsupported in the record or clearly erroneous, see Fed.R.Civ.P. 52(a). We thus accept them as correct. These findings provide considerable support for the district court’s conclusion that the defendants successfully rebutted the government’s prima facie case. Because the defendants also provided compelling evidence on ease of entry into this market, we need not decide whether these findings, without more, are sufficient to rebut the government’s prima facie case. The foregoing analysis of non-entry factors is intended merely to underscore that, contrary to the government’s assumption, these factors are relevant, and can even be dispositive, in a section 7 rebuttal analysis.
II.
The existence and significance of barriers to entry are frequently, of course, crucial considerations in a rebuttal analysis. In the absence of significant barriers, a company probably cannot maintain supra-competitive pricing for any length of time.
See, e.g., United States v. Falstaff Brewing Corp.,
As authority for its “quick and effective” entry test, the government relies primarily on
United States v. Waste Management, Inc.,
That the “quick and effective” standard lacks support in precedent is not surprising, for it would require of defendants a degree of clairvoyance alien to section 7, which, as noted above, deals with probabilities, not certainties. Although the government disclaims any attempt to impose upon defendants the burden of proving that entry actually will occur, see Reply Brief for Appellant at 13 n. 13, we believe that an inflexible “quick and effective” entry requirement would tend to impose precisely such a burden. A defendant cannot realistically be expected to prove that new competitors will “quickly” or “effectively” enter unless it produces evidence regarding specific competitors and their plans. Such evidence is rarely available; potential competitors have a strong interest in downplaying the likelihood that they will enter a given market. When the government sarcastically “wonders how slow and ineffec *988 tive entry rebuts a prima facie case,” id. at 12, it misses a crucial point. If the totality of a defendant’s evidence suggests that entry will be slow and ineffective, then the district court is unlikely to find the prima facie case rebutted. This is a far cry, however, from insisting that the defendant must invariably show that new competitors will enter quickly and effectively.
Furthermore, the supposed “quick and effective” entry requirement overlooks the point that a firm that
never
enters a given market can nevertheless exert competitive pressure on that market. If barriers to entry are insignificant, the
threat
of entry can stimulate competition in a concentrated market, regardless of whether entry ever occurs.
See Falstaff Brewing,
The final flaw in the proposed “quick and effective” standard is its manipulability. The adjectives “quick” and “effective” are not self-defining, and have not traditionally been used in the section 7 context. The government’s Merger Guidelines do not use the words when discussing entry, noting only that
[i]f entry into a market is so easy that existing competitors could not succeed in raising price for any significant period of time, the Department is unlikely to challenge mergers in that market.... In assessing the ease of entry into a market, the Department will consider the likelihood and probable magnitude of entry in response to a “small but significant and nontransitory” increase in price.
Guidelines § 3.3, reprinted in 4 Trade Reg.Rep. (CCH) at 20,562. In its brief, moreover, the government fails to state its own standard consistently, insisting at one point that a defendant show that entry will be “sure, swift, and substantial.” Brief for Appellant at 16. Our uncertainty over the meaning and implications of “quick and effective” entry makes us all the more resistant to the imposition of such a requirement. Nor has the government shown that current section 7 law is so confused as to warrant the invention of a new standard.
The government’s insistence on a “quick and effective” entry standard only reaffirms our doubts, raised in section I of this opinion, about the government’s approach to section 7 analysis. Predicting future competitive conditions in a given market, as the statute and precedents require, calls for a comprehensive inquiry. The government’s standard would improperly narrow the section 7 inquiry, channelling what should be an overall analysis of competitiveness into a determination of whether a defendant has shown particular facts.
Having rejected the “quick and effective” entry standard itself, we turn briefly to the government's more general argument that the district court’s findings regarding ease of entry failed to support its conclusion that the defendants had rebutted the prima facie case. The district court in this case discussed a number of considerations that led it to conclude that entry barriers to the United States HHUDR market were not high enough to impede future entry should Tamrock’s acquisition of Secoma lead to supracompetitive pricing. First, the court noted that at least two companies, Cannon and Ingersoll-Rand, had entered the United States HHUDR market in 1989, and were poised
*989
for future expansion.
8
In sum, we see no error — legal or factual — in the district court’s determination that entry into the United States HHUDR market would likely avert anticompetitive effects from Tamrock’s acquisition of Seco-ma. The court’s determination on entry, considered along with the findings discussed in section I of this opinion, suffices to rebut the government’s prima facie case.
III.
Finally, we consider the strength of the showing that a section 7 defendant must make to rebut a prima facie case. The district court simply reviewed the evidence that the defendants presented and concluded that the acquisition was not likely to substantially lessen competition. The government argues that the court erred by failing to require the defendants to make a “clear” showing. See Brief for Appellant at 13. The relevant precedents, however, suggest that this formulation overstates the defendants’ burden. We conclude that a “clear” showing is unnecessary, and we are satisfied that the district court required the defendants to produce sufficient evidence.
The government’s “clear showing” language is by no means unsupported in the case law. In the mid-1960s, the Supreme Court construed section 7 to prohibit virtually any horizontal merger or acquisition. At the time, the Court envisioned an ideal market as one composed of many small competitors, each enjoying only a small market share; the more closely a given market approximated this ideal, the more competitive it was presumed to be.
See United States v. Aluminum Co. of Am.,
This perspective animated a series of decisions in which the Court stated that a section 7 defendant’s market share measures its market power, that statistics alone establish a prima facie case, and that a defendant carries a heavy burden in seeking to rebut the presumption established by such a prima facie case. The Court most clearly articulated this approach in Philadelphia Bank:
Th[e] intense congressional concern with the trend toward concentration [underlying section 7] 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.
In
United States v. Von’s Grocery Co.,
Although the Supreme Court has not overruled these section 7 precedents, it has cut them back sharply. In
General Dynamics,
General Dynamics
began a line of decisions differing markedly in emphasis from the Court’s antitrust cases of the 1960s. Instead of accepting a firm’s market share as virtually conclusive proof of its market power, the Court carefully analyzed defendants’ rebuttal evidence.
12
These cases dis
*991
carded
Philadelphia
Bank's insistence that a defendant “clearly” disprove anti-competitive effect, and instead described the rebuttal burden simply in terms of a “showing.”
See, e.g., United States v. Marine Bancorporation,
In the aftermath of
General Dynamics
and its progeny, a defendant seeking to rebut a presumption of anticompetitive effect must show that the prima facie case inaccurately predicts the relevant transaction’s probable effect on future competition.
See American Stores,
By focusing on the future, section 7 gives a court the uncertain task of assessing probabilities. In this setting, allocation of the burdens of proof assumes particular importance. By shifting the burden of producing evidence, present law allows both sides to make competing predictions about a transaction’s effects. If the burden of production imposed on a defendant is unduly onerous, the distinction between that burden and the ultimate burden of persuasion — always an elusive distinction in practice — disintegrates completely. A defendant required to produce evidence “clearly” disproving future anticompetitive effects must essentially persuade the trier of fact on the ultimate issue in the case — whether a transaction is likely to lessen competition substantially. Absent express instructions to the contrary, we are loath to depart from settled principles and impose such a heavy burden.
See Kaiser Aluminum & Chem. Corp. v. FTC,
*992
Imposing a heavy burden of production on a defendant would be particularly anomalous where, as here, it is easy to establish a prima facie case. The government, after all, can carry its initial burden of production simply by presenting market concentration statistics. To allow the government virtually to rest its case at that point, leaving the defendant to prove the core of the dispute, would grossly inflate the role of statistics in actions brought under section 7. The Herfindahl-Hirschman Index cannot guarantee litigation victories.
13
Cf
. Ball Memorial Hosp.,
The appellees in this case presented the district court with considerable evidence regarding the United States HHUDR market. The court credited the evidence concerning the sophistication of HHUDR consumers and the insignificance of entry barriers, as well as the argument that the statistics underlying the government’s prima facie case were misleading. This evidence amply justified the court’s conclusion that the pri-ma facie case inaccurately depicted the probable anticompetitive effect of Tam-rock’s acquisition of Secoma. Because the government did not produce sufficient evidence to overcome this successful rebuttal, the district court concluded that “it is not likely that the acquisition will substantially lessen competition in the United States either immediately or long-term.”
For the foregoing reasons, the judgment of the district court is
Affirmed.
Notes
. Section 7 prohibits mergers and acquisitions the effect of which “may be substantially to lessen competition, or to tend to create a monopoly.” 15 U.S.C. § 18.
. The parties in this case do not seriously contest the district court’s definition of the relevant markets. The court defined the geographic market as the entire United States,
see
Although the appellees quibble with the court's product market definition, they conclude that "the [district] court’s product market definition presages its finding that the extent of present competition and ease of entry preclude finding a violation of Section 7." Brief for Appellees at 10 (emphasis added). If the appel-lees believe that the court’s product market definition contributed to their victory, we see no reason to address their halfhearted and contradictory challenges to that definition.
. From 1986 through 1988, Tamrock had an average 40.8% share of the United States HHUDR market, while Secoma’s share averaged 17.5%.
. Even if we found more impressive the argument that the district court did not clearly articulate the legal standard applicable to a section 7 rebuttal, it would remain open to us to affirm that court’s judgment.
Cf. Nelson v. United States,
.
See Brown Shoe Co. v. United States,
.
See also id.
at 322 n. 38,
. See also supra note 3 (HHI of United States HHUDR market before merger was 2878; Department of Justice regards any market in which HHI exceeds 1800 as "highly concentrated”).
. As the Guidelines note, “ ‘Entry’ may occur as firms outside the market enter for the first time or as fringe firms currently in the market greatly expand their current capacity." Guidelines § 3.3, reprinted in 4 Trade Reg.Rep. (CCH) at 20,562 n. 20 (emphasis added).
. Some of these firms have already tried, but failed, to penetrate the United States HHUDR market. As the district court correctly noted, however, failed entry in the past does not necessarily imply failed entry in the future: if prices reach supracompetitive levels, a company that has failed to enter in the past could become competitive.
See
.The court, for instance, noted that HHUDRs are custom-made, and thus are not readily interchangeable or replaceable. Buyers, therefore, tend to return to sellers from whom they have purchased in the past.
. Justice Stewart, in dissent, emphasized the considerable amount of evidence in the record indicating the market's competitiveness.
. Judge Posner has elucidated this point:
The most important developments that cast doubt on the continued vitality of such cases as Brown Shoe and Von’s are found in other cases, where the Supreme Court, echoed by *991 the lower courts, has said repeatedly that the economic concept of competition, rather than any desire to preserve rivals as such, is the lodestar that shall guide the contemporary application of the antitrust laws, not excluding the Clayton Act.... Applied to cases brought under Section 7, this principle requires the district court ... to make a judgment whether the challenged acquisition is likely to hurt consumers, as by making it easier for the firms in the market to collude, expressly or tacitly, and thereby force price above or farther above the competitive level.
Hospital Corp. of Am. v. FTC,
. We refer the government to its own Merger Guidelines, which recognize that “[i]n a variety of situations, market share and market concentration data may either understate or overstate the likely future competitive significance of a firm or firms in the market.” Guidelines § 3.2,
reprinted in
4 Trade Reg.Rep. (CCH) at 20,561. Although the Guidelines disclaim “slavish[ ] adherence]" to such data,
id.,
statement,
reprinted in 4
Trade Reg.Rep. (CCH) at 20,552, we fear that the Department of Justice has ignored its own admonition. The government does not maximize its scarce resources when it allows statistics alone to trigger its ponderous enforcement machinery.
Cf. Syufy Enters.,
