This appeal presents important questions of antitrust law. The central issue is whether the August 1966 acquisition of Amerock Corporation by The Stanley Works violated § 7 of the Clayton Act1 and § 5 of the Federal Trade Commission Act.2 The Federal Trade Commission held that it did and ordered divestiture.3 Stanley filed a petition asking this Court to review and set aside the Commission’s order. See 15 U.S.C. § 45(c). For the reasons given below, we believe the effect of the merger may be substantially to lessen actual competition in the national cabinet hardware market. Accordingly, we affirm the decision of the Commission and direct that its order be enforced.
I.
As always, resolution of a question of antitrust illegality requires us to describe the companies involved, analyze the product and geographic market in which they compete, and explore the structure of the industry affected by the merger, to the end that we may properly assess the probable effects of the merger on competition.
The Companies
Stanley is a Connecticut corporation engaged in the manufacture and sale of hand and power tools, hardware products, steel and steel strapping, with its principal place of business in New Britain, Connecticut. It is a large, multi-plant, multi-product concern with a history of expanding sales. In 1965, a year prior to the merger, Stanley’s domestic sales were $123,000,000, an increase of $29,-000,000 over its 1963 sales figures. For the period 1963-1965, its net earnings after taxes rose from $4,200,000 to $6,~ 600,000, an advance of more than 57%. In 1965 Stanley’s sales in the- relevant product market4 were $814,000. It operated numerous production facilities, including plants located in California, Connecticut, Florida, New Jersey, North Carolina, Ohio, Tennessee, Vermont and Illinois.
Amerock was incorporated in 1928 and maintains its principal place of business in Rockford, Illinois. At the time of this merger, Amerock was engaged in the manufacture and sale of certain hardware products for use primarily in kitchens, in addition to a broad line of window, appliance, furniture and general household hardware products. Its do*500mestic sales in 1963 totaled $23.8 million, and increased by 1965 to $29.4 million, an advance of more than 23%. Amerock’s 1965 net earnings after taxes were $2.8 million, a gain of over 47% over its 1963 earnings figures. Ame-rock’s 1965 sales in the relevant product market were in excess of $18,000,000.
The Industry ■
Since Section 7 of the Clayton Act forbids mergers between companies “in any line of commerce in any section of the country,” when the merger may result in substantial lessening of competition, determination of the relevant product and geographic markets is of critical significance. See, e. g., Brown Shoe Co. v. United States, 370 U.S. 294, 325, 82 S.Ct. 1502, 8 L.Ed.2d 510 (1962). Here the task of isolating the relevant markets has been made simpler for us, since Stanley and the Commission stipulated that within the general hardware industry, sales of cabinet hardware products in the Nation constitute the appropriate product and geographic markets. The parties agreed also that for purposes of this case, there are no relevant product or geographic submarkets. The Examiner and the Commission grounded their findings of fact on these stipulations; their findings are conclusive, if supported by substantial evidence. 15 U.S.C. § 45(c).
The parties are agreed that cabinet hardware includes pulls, knobs, hinges, latches, catches and similar products, including drawer slides and shelving hardware, used principally in kitchen cabinets. The cabinet hardware market comprises two related lines, residential cabinet hardware and architectural, or institutional, cabinet hardware.5 Residential cabinet hardware is used in houses and apartments. At one time, residential cabinet hardware was made primarily of metal stampings and extrusions, and was essentially functional in nature, with simple lines and designs. In the years following World War II, as the American home began to reflect post-war economic affluence, consumer demand for more highly ornamented cabinet hardware designs increased, and the industry underwent a dramatic change. Manufacturers of residential cabinet hardware turned to a zinc die-casting process, and, as a result, products in this line were transformed into highly stylized, fashion-oriented items, which were offered in a wide variety of designs and finishes to complement the motifs of contemporary cabinet work. Virtually all residential knobs and pulls are now made by the die-casting method. This enables manufacturers to produce the intricate styles and designs demanded by consumers of residential cabinet hardware.
Architectural cabinet hardware is produced for use in institutional and commercial buildings, such as schools, recreational centers and office buildings. The marketing watchword of architectural cabinet hardware is embodied in the phrase, “form follows function;” products in this line must be more durable than residential cabinet hardware in order to withstand the heavier wear to which they are subject in an institutional or commercial setting. As a result, architectural cabinet hardware is rarely made by the die-cast method but is stamped out of bronze, brass, aluminum or steel. These metals are more durable than zinc die-cast material and also more expensive.
Market Shares
Cabinet hardware sales in the United States in 1965, a year prior to the merger, were between $76,000,000 and $80,-000,000. The record discloses that in 1965, Stanley ranked as the tenth leading producer of cabinet hardware products with sales of $814,000, representing a market share of 1%. Amerock, the acquired company, ranked first as the sell*501er of cabinet hardware products in the United States. Its 1965 sales exceeded $18,000,000, and the company controlled 22-24% of the market.6
The Commission upheld the Trial Examiner’s finding that the cabinet hardware industry was concentrated. As the table in the margin indicates, the four leading firms in the industry accounted for total sales ranging from 49% to 51% of the market.7
II.
Our attention initially must focus on a threshold dispute between the parties. It is Stanley’s contention that the rationale and critical findings of the Commission’s decision indicate that the Stanley-Ameroek merger was declared illegal solely on the ground that the merger eliminated potential competition in the cabinet hardware market. The Commission opposes this characterization of its decision and insists that elimination of both actual and potential competition triggered application of Clayton § 7 to the merger. The Commission’s position on appeal is that either ground for its decision adequately made out a violation of the Clayton Act in this ease. The argument is of central importance because under the rule enunciated in SEC v. Chenery Corp., 318 U.S. 80, 92, 63 S.Ct. 454, 87 L.Ed. 626 (1943), we must find that the considerations urged on appeal in support of the Commission’s order are tion was based, if we are to sustain the order.
Chenery instructs that “the orderly functioning of the process of review requires that the grounds upon which the administrative agency acted be clearly disclosed and adequately sustained.” Chenery, supra, 318 U.S. at 94, 63 S.Ct. at 462. It is clear to us that the Commission’s decision was dual pronged and that the Stanley-Ameroek merger was invalidated on both actual and potential competition grounds. And in our view, the actual competition case was “clearly disclosed” within the meaning of Chen-ery.8
*502We do not develop a “new ground” for the Commission’s holding, as the dissent mistakenly suggests, but find the actual competition ease clearly underscored in the proceedings before the Examiner, and also in the opinion rendering the Commission’s decision. The complaint charged that as a result of the merger “substantial actual and potential competition has been, or may be, eliminated.” Stanley’s clear perception that an actual competition theory had been litigated before the Trial Examiner is evident from its brief on appeal to the Commission which discussed the merits of the actual competition case at some length.9
To preserve the integrity both of judicial review and of agency procedures we must be persuaded not only that Stanley had notice of the actual competition theory, but that the Commission specifically adopted the actual competition case as a reason for its decision. Any doubts on that score, however, are convincingly dispelled by a careful reading of the Commission’s opinion, which repeatedly relates the effect of the merger on actual competition.
The Commission adopted at the outset the Examiner’s finding that “the merger between Stanley and Amerock led to increased concentration in the already concentrated cabinet hardware market as well as eliminating Amerock as the leading independent producer of cabinet hardware . . . . ” Unmistakably this is the argot of an actual competition case.
Moreover, that portion of the Commission’s opinion which discussed the competitive effects of the Amerock acquisition articulated the Commission’s overall view of the case in language that indicates beyond doubt the mix of actual and potential competition theories underlying the Commission’s decision. It was the Commission’s view that the “case presents ... a mingling of the effects which are traditionally cognizable under the discrete categories of actual and potential competition.” After reviewing Stanley’s role in the cabinet hardware market, the Commission characterized Stanley as both “an actual and potential competitor in the stipulated market.” “Viewing the case in this light,” the Commission concluded, “and within the general confines of the established analytical framework relating to actual and potential competition, we are convinced from the present record that the examiner was correct in concluding that the merger of Stanley and Amerock had significant anticompetitive consequences proscribed by Section 7 . . ”
In addition, the Commission’s opinion (footnote 12), establishes clearly that the elimination of actual competition was a ground on which the Commission’s decision rested. Noting that the examiner had concluded that the cabinet hardware market was concentrated, the Commis*503sion cited two studies10 which bolstered that finding. The opinion sets forth the view shared by a number of scholars that “any horizontal acquisition involving a firm with more than 20% of the relevant market [Amerock’s share wás 22-24%] should be deemed illegal,” and refers to authorities which support that view.11 Both sources, at the cited pages, clearly address themselves to cases in which mergers eliminated actual competition.
Finally, and most convincingly, the Commission emphasized the importance of closely scrutinizing mergers in markets that are already concentrated, relying on United States v. Philadelphia National Bank, 374 U.S. 321, 83 S.Ct. 1715, 10 L.Ed.2d 915 (1963). The question in that case was whether a merger between Philadelphia National Bank and Girard Trust Corn Exchange Bank, the second and third largest commercial banks in the Philadelphia metropolitan area, violated § 7 by lessening competition in the commercial banking business. The Court held that it did, and grounded its decision on the elimination of actual competition. The Commission clearly understood and considered the rationale of the case, and applied it to the Stanley-Ame-rock merger.
In light of the above, we would be remiss in our duty as a reviewing court if we abstained from considering the merits of the actual competition theory and remanded the ease to the Commission, as Stanley urges us to do. The record contains ample evidence to enable this Court to assess the merits, and it is abundantly clear that the Commission relied on the actual competition theories, among others, in reaching its conclusion. Chenery does not predicate judicial review of an agency finding on the correctness of that finding, nor does it require an agency to crystallize its basis of decision into a single, rarefied reason. All that is required is that “ [i] f the administrative action is to be tested by the basis upon which it purports to rest, that basis must be set forth with such clarity as to be understandable.” SEC v. Chenery Corp. (Chenery II), 332 U.S. 194, 196, 67 S.Ct. 1575, 1577, 91 L.Ed. 1995 (1947). We believe the Commission’s decision with respect to the actual competition case satisfies that test.
III.
Having reached the merits, we must decide whether the effect of the merger “may be substantially to lessen competition” in the cabinet hardware market. Mindful of the admonition that questions of antitrust law are not always “susceptible of a ready and precise answer”, United States v. Philadelphia National Bank, supra,, 374 U.S. at 362, 83 S.Ct. at 1741, we take as our starting point, and touchstone of analysis, that “[t]he dominant theme pervading congressional consideration of the 1950 amendments [to § 7] was a fear of what was considered to be a rising tide of economic concentration in the American economy.” Brown Shoe Co. v. United States, 370 U.S. 294, 315, 82 S.Ct. 1502, 1518, 8 L.Ed.2d 510 (1962). And we recognize “that a keystone in the erection of a barrier to what Congress saw was the rising tide of economic concentration, was [§ 7’s] provision of authority for arresting mergers at a time when the trend to a lessening of competition in a line of commerce was still in its incipiency. Congress saw the process of concentration in American business as a dynamic force; it sought to assure the Federal Trade Commission and the courts the power to brake this force at its outset and before it gathered momentum.” Id. at 317-318, 82 S.Ct. at 1520.
Unlike the factual settings presented in Brown Shoe, supra, United States v. Von’s Grocery, 384 U.S. 270, 86 S.Ct. 1478, 16 L.Ed.2d 555 (1960), and United States v. Pabst Brewing Co., 384 *504U.S. 546, 86 S.Ct. 1665, 16 L.Ed.2d 765 (1966), where an analysis of the relevant market structure revealed only a trend toward concentration, the Commission clearly found here that the relevant market was already concentrated. Stanley argues, however, that the failure to find a trend toward concentration takes this case out of the line of Brown, Von’s and Pabst, decisions which held horizontal mergers between actual competitors invalid. But United States v. Continental Can, 378 U.S. 441, 84 S.Ct. 1738, 12 L.Ed. 2d 953 (1964), teaches that where a market is already concentrated any merger between market leaders is suspect. The court said:
[W]here there has been a “history of tendency toward concentration in the industry” tendencies toward further concentration “are to be curbed in their incipiency.” Brown Shoe Co. v. United States, 370 U.S., at 345, 346, 82 S.Ct. [1502] at 1535. Where “concentration is already great, the importance of preventing even slight increases in concentration and so preserving the possibility of eventual deeoncentration is correspondingly great.” United States v. Philadedphia National Bank, 374 U.S. 321, 365, n. 42, 83 S.Ct. 1715, 1742 [10 L.Ed.2d 915]; United States v. Aluminum Co. of America, [377 U.S. 271, 84 S.Ct. 1283, 12 L.Ed.2d 314 (1964)]. United States v. Continental Can, supra, 378 U.S. at 461-462, 84 S.Ct. at 1749.12
We have indicated that the four leading firms in the cabinet hardware industry dominated 49-51% of the market. The Examiner and the Commission thought these figures reflected market concentration. We agree that the industry is sufficiently concentrated to invoke the proscriptive sanction of the Clayton Act under the circumstances of this case.13
The relevant literature strongly supports this view.14 To mention only one example, Kaysen and Turner describe a “tight oligopoly” as an industry in which eight firms or less supply 50% of the market, with the largest firms controlling 20% or more.15 Under their analysis, the cabinet hardware market falls *505well within the economic parameters which describe a concentrated market.
Most persuasive of all in our view, however, is the unanimity reached by the trial examiner and the Commission in holding this market concentrated. In view of the Commission’s expertise in assessing the impact of business practices on economic market forces, we believe its judgment as to what type of market is concentrated for antitrust purposes is entitled to substantial weight.16
Upon its review of all the evidence, the Commission concluded that
the very reasons leading Stanley to acquire Ameroek are the same reasons which support the charge in this case that the merger will have significant anticompetitive effects. Stanley acquired Ameroek precisely because it was the dominant company in the market . . . and because it believed that the acquisition would further entrench Amerock’s already dominant position, while any other course designed to achieve Stanley’s goals in the cabinet hardware market —internal expansion by Stanley or acquisition of a smaller company in the industry — would only stir up competition.
There was substantial evidence in the record to support that view. Among the evidence we find a Stanley Hardware Division task force report, prepared on June 10, 1964, as part of a study of possible new ventures for the Hardware Division, which concluded:
it is felt that a strong Stanley entry into parts of the cabinet hardware market via product development could be expected to accentuate industry-wide declines in prices and profits. A strong properly oriented Stanley entry into the market via acquisition could, on the other hand, be designed to contribute to a reversal in the downward trend in prices and profits.
In the general hardware industry, in which most of Stanley’s business was transacted, it was not only the leading firm, but a price leader as well. A long-range Stanley Hardware Division report, prepared in mid-1965, stated: “As the largest firm in the industry, the Hardware Division must continue to show leadership in the important area of pricing policy. As conditions warrant, we must continue to take the initiative and corresponding risks of being the first within the industry to raise prices and attempt to keep them at such higher levels.” This policy undoubtedly presented a threat to the future competitive vitality of the industry, which had recently experienced price decreases.
In light of these disclosures, the Commission justifiably was apprehensive that the Stanley-Amerock merger, by increasing concentration at the top of the market, might have a “tipping effect” in the cabinet hardware industry, turning a concentrated market manifesting limited signs of price competition into a rigid, lifeless market tending toward even greater concentration and economic enervation. A market as delicately balanced as this, such that a merger between the first and tenth ranking firms threatens substantial anti-competitive consequences, is “concentrated” by any measure. Section 7’s incipiency standard, which “requires not merely an appraisal of the immediate impact of the merger upon competition, but a prediction of its impact upon competitive conditions in the future”,17 provides preventive as well as remedial therapy for an ailing industry; surely its salutary medicines need not be withheld until the diagnosis reads “terminal.”
Stanley argues that foreclosure of a de minimis share of a market *506bars application of § 7, and that the competitive overlap between Stanley and Amerock in this case was de minimis. Our dissenting brother has adopted this view, but has based his conclusion on an altogether erroneous analysis of market shares. After parsing the stipulated product market, he proceeds to treat residential cabinet hardware and institutional cabinet hardware as distinct lines of commerce, thereby ignoring the clear agreement between the parties that no product or geographic submarkets exist in the cabinet hardware industry. He then announces, virtually ex cathedra, that the degree of competitive overlap existing between Stanley and Amerock amounted to a mere .35% of the market. The dissent concludes that the percentage of the market affected by the merger is de minimis and, on that account, Stanley’s acquisition of Amerock survives even the most critical antitrust scrutiny. In light of the stipulation, we regard the dissent’s method of analysis as puzzling. It is also dangerous for it may have the effect of both dissuading litigants from agreeing upon facts and deterring agencies from acting on those agreed stipulations of fact. No amount of statistical legerdemain justifies disregarding the binding stipulation that controls this case, under which the relevant product market is defined as the entire cabinet hardware industry and Stanley’s market share is agreed to as constituting 1% of total sales. The parties conceded those facts, the Examiner acted upon those facts, and the Commission based its decision on those facts. There may have been strategic litigation tradeoffs that led to the adoption of the stipulation; but we shall never know. Nor can we guess what posture this case would have assumed had there been no stipulation. What constellation of facts might have emerged, but for the stipulation, is wholly a matter of surmise, in which we may not permit ourselves to engage. Having agreed on a set of facts, the parties, and this Court, must be bound by them; we are not free to pick and choose at will. While we recognize that § 7 can tolerate de minimis foreclosure, Brown Shoe Co. v. United States, 370 U.S., at 329, 82 S.Ct. 1502, 8 L.Ed.2d 510, we cannot agree that the competition eliminated by this merger was sufficiently insubstantial to purge it of illegality under the Clayton Act.
Although the market shares involved here do not precisely match market shares in any case cited to us by either Stanley or the Commission — rarely are two antitrust cases alike — we believe that the rationale underlying at least two Supreme Court decisions indicates that Stanley’s 1% is not a de minimis share of the cabinet hardware market. Most persuasive is United States v. Pabst Brewing Co., 384 U.S. 546, 86 S.Ct. 1665, 16 L.Ed.2d 765 (1966), in which a merger between two companies engaged in the manufacture, sale and distribution of beer was held invalid under § 7 because it eliminated competition in three markets, including the national market.18 In the national market, Pabst ranked tenth among the leading firms, with 3.02% of the market; Blatz, the acquired company, ranked eighteenth with 1.47%. The relevant product market, though tending toward concentration, was not nearly as solidified as the market in this case: in 1957, one year prior to the Pabst-Blatz merger, 10 companies controlled 45.06% of the market; in 1961, ten companies controlled 52.6% of the market. Even after taking into account the trend toward concentration, competition in the product market in Pabst appears robust in comparison to the cabinet hardware market, in which four firms control approximately 50% of the *507market. In view of this market concentration in the sale of cabinet hardware products, we cannot assume, as Judge Mansfield does, that a difference of less than one-half of one per cent — the difference between Blatz’s 1.47% and Stanley’s 1% market shares — is of decisive significance for a question of such controlling importance as whether 1% market control is, or is not, de minimis.
Stanley’s rank in the industry also contributes to the conclusion that its 1 % share of the market is not insubstantial. The Supreme Court noted in United States v. Aluminum Co. of America, 377 U.S. 271, 84 S.Ct. 1283, 12 L.Ed.2d 314 (1964), that central to the underlying philosophy of § 7, as amended, is the principle “that competition will be most vital ‘when there are many sellers, none of which has any significant market share.’ United States v. Philadephia National Bank, 374 U.S. at 363, 83 S.Ct. 1715, 10 L.Ed.2d 915.” United States v. Aluminum Co. of America, supra, 377 U.S. at 280, 84 S.Ct. at 1289. But the greater the concentration in the market “the greater is the likelihood that parallel policies of mutual advantage, not competition, will emerge. That tendency may well be thwarted by the presence of small but significant competitors.” Ibid.19 In Alcoa, the Court specially noted that no more than a dozen companies could account for as much as 1% of industry production and therefore Rome, ranking ninth with 1.3% of the market, was a substantial competitor.20 Stanley, like Rome, is a small but significant competitor in a market with few sellers. Based on the record in this case, only ten companies, of which Stanley was tenth, accounted for 1% or more of the cabinet hardware market. We cannot say, therefore, that under the circumstances involved here, Stanley’s 1% share was insubstantial.21
*508Finally, we note that though a market may be concentrated, forces may operate so as to maintain some level of competition and thus preserve the possibility of eventual deconcentration. That is why the continued independence of companies with relatively small market shares is so crucial to the health and vitality of a market threatening to become oligopolistic.22 Not only was Stanley an active competitor in the cabinet hardware market at the time it acquired Ameroek but the record indicates that Stanley would have been a more active competitor in the future, absent merger.23 For all the reasons set forth, it is clear to us that the elimination of competition resulting from the merger was substantial and not de minimis, within the meaning of § 7’s prohibitions.
We cannot conclude without observing that our dissenting brother incorrectly reads our opinion as announcing a rule of per se illegality for horizontal mergers. This is regrettable for nothing we decide today remotely hints at such a conclusion. The law is clear in its teaching that in an already concentrated industry with few sellers, in which the four leading companies dominate approximately 50% of the market, a merger involving the leading firm, controlling 22-24% of the market, with a firm like Stanley, would seriously threaten substantial anti-competitive consequences. This merger cannot survive in the face of the Clayton Act and its history. Accordingly, we affirm the Commission’s order and direct its enforcement.24
. 15 U.S.C. § 18. Section 7 as amended, provides:
“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 any 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.”
. 15 U.S.C. § 45(a) (1). That section provides :
“Unfair methods of competition in commerce, and unfair or deceptive acts or practices in commerce, are declared unlawful.”
The complaint in this case, issued against Stanley on April 30, 1968, charged a violation of Clayton § 7 and Federal Trade Commission Act, § 5. The Commission found that the merger transgressed both statutes. Although a violation of § 5 is not necessarily a violation of § 7, see Federal Trade Commission v. Sperry Hutchinson, 405 U.S. 233, 246, 92 S.Ct. 898, 31 L.Ed.2d 170 (1972), it is the case that every violation of § 7 is''also a violation of § 5. Since we hold that the Stanley-Ameroek merger is illegal under § 7, and therefore illegal under § 5, we need not give special consideration to § 5 analysis.
. The Commission’s decision was rendered on May 17, 1971.
. For our discussion of the relevant product market see p. 500.
. We stress that neither of these lines constitutes a separate product market for . purposes of this case, an element ignored in the dissenting opinion. Our division of the market at this point is designed to serve descriptive, not analytic, purposes.
. The respective totals in cabinet hardware sales, and Stanley’s and Amerock’s percentage market shares, were agreed to by stipulation.
. 1965
Cabinet Hard-
ware Sales Total
in U. S. Assets
1. Amerock Corp................... ..... $18,218,474 25,133,914
2. National Lock Company ........... ..... $11,499,445 37,992,215
3. Ajax Hardware Corp.............. ...... $ 6,798,000 3,338,412
4. Knape & Vogt Mfg. Co........... .....$ 6,013,304 7,968,450
5. Jaybee Mfg. Corp................ ...... $ 3/056,673 1,710,989
6. Grant Pulley & Hardware Corp...... 2,369,165
7. David Allison Co., Inc........... ...... $ 1,500,000 1,500,000
8. Tassell Industries, Inc............ ..... $ 1,408,600 2,483,424
9. Hyer Hardware Mfg. Corp....... ...... $ 1,344,464 524,452
10. Stanley Hardware Division ........ ..... $ 814,000 125,926,000
. Stanley’s position is that the Commission’s potential competition theory is inadequate to support a finding of merger illegality in this case. The Commission held that Stanley was a reasonably probable entrant into the residential cabinet hardware market, and that Stanley would have entered by internal development had it not acquired Amerock. In the Commission’s view, the merger eliminated Stanley as a potential entrant, removed the “disciplining effect” it exercised on the market, and raised barriers to entry in an already concentrated market. The Commission did not find that Stanley was the “most likely entrant,” see FTC v. Procter & Gamble, 386 U.S. 568, 581, 87 S.Ct. 1224, 18 L.Ed.2d 303 (1967); cf. United States v. El Paso Natural Gas, 376 U.S. 651, 658-659, 84 S.Ct. 1044, 12 L.Ed.2d 12 (1964). In addition, the Commission did not point to any evidence indicating that Stanley exercised a “disciplining effect” on the market, nor did *502it illustrate how Stanley’s acquisition of Amerock would contribute to raising barriers to entry in the residential cabinet hardware industry. Inasmuch as we conclude that the Stanley-Amerock merger is illegal because it eliminated substantial actual competition and thereby may lessen competition in the cabinet market as a whole, we need not decide the merits of the potential competition ease.
Thus, in this part of our opinion, we consider Stanley’s argument that the actual competition theory was not “adequately disclosed”. In Part III, we shall treat the question whether that ground is “adequately sustained” by substantial evidence.
Thus, to note only a few examples, at page 23 of its brief Stanley argued that “[t]he so-called ‘horizontal’ aspects of the case, i. e., the amount of actual competition in cabinet hardware eliminated by the merger, is de minimis, and the Examiner erred in not so finding.” At pages 25-26 of its brief, Stanley argued that the examiner had incorrectly assessed “the amount of actual competition in fact eliminated by the merger.” And finally Stanley asserted that “[i]n view of all the considerations summarized above [at pages 23-30 of its brief], it is clear that the horizontal aspect of this case is quite different from the situations involved in the leading horizontal cases
. K. Kaysen & D. Turner, Antitrust Policy: An Economic and Legal Analysis 72 (1959), and J. Bain, Industrial Organization 14-41 (2d ed. 1968).
. K. Kaysen & D. Turner, supra, at 133; Stigler, Mergers and Preventive Antitrust, 114 U.Pa.L.Rev. 176, 182 (1955).
. Our dissenting brother ignores this admonition, and would confine the power of antitrust enforcement agencies to cases where a “trend” toward concentration in the industry has been proven. In doing so, he disregards the teaching of Continental Can that actual concentration is a far more insidious base upon which to build a merger. This would seem to pay greater heed to the symptom than the disease.
. Stanley insists that such a market is not “concentrated.” They cite Justice Department Merger Guidelines, see 1 Trade Reg. Law Rep. K 4510, which indicate that a market is highly concentrated when shares of the four largest firms account for 75% or more of the market. But as often proves true, reading on to the end of a sentence can be instructive. It appears that the Department of Justice will ordinarily challenge mergers in a “highly concentrated market” where the acquired and acquiring firm account for 1% and 15% of the market respectively, 1 Trade Reg. Law Rep. ¶ 4510 at 6884. But the Department also characterizes some markets as “less highly concentrated” — markets in which the four leading firms account for less than 75% of the market. Under such conditions the Department will ordinarily challenge mergers when the parties account for 1% and 25% of the market. Stanley controlled 1% of the cabinet hardware market; Amerock 22-24%. It should be evident that market shares in this case are sufficiently close to the Department guidelines to cause us to hesitate before accepting Stanley’s view.
. Although the teachings of scholars cannot be dispositive, it would be foolhardy, in an area as complicated as this, to wholly disregard the lessons they have learned in a lifetime of study.
. Kaysen & Turner, supra, at 72. The authors define economic markets in terms of four levels of concentration. A “dominant firm” or “partial monopoly” market is one in which a single large firm supplies 60% of the market and no other seller supplies a significant portion of the demand. “Tight oligopoly” is the next level of concentration. See also Bain, Industrial Organization 131 (2d ed. 1968). (Market in which four firms control 50% reflects high-moderate concentration.)
. Stanley’s own partial reliance on Justice Department Merger guidelines, discussed at note 13, supra, reflects this same view. Stanley concedes that the Justice Department’s view expressed in its guidelines should be given special weight; so too, we believe, should the Commission’s views.
. United States v. Philadelphia National Bank, supra, 374 U.S. at 362, 83 S.Ct. at 1741.
. The relevant geographic markets in Pabst were Wisconsin, the Tri-State market consisting of Wisconsin, Michigan and Illinois, and the Nation. The Court held that “the evidence as to the probable effect of the merger on competition in Wisconsin, in the three-state area, and in the entire country was sufficient to show a violation of § 7 in each and all of these three areas.” 384 U.S., at 552, 86 S.Ct., at 1669.
. The Court found that Alcoa’s acquisition of Rome Cable Corporation was reasonably likely to result in a substantial lessening of competition in the highly, concentrated aluminum conductor industry where 5 companies controlled 76% of the relevant market. Alcoa was the leading producer of aluminum conductor, with 27.8% of the market; Rome was ninth with 1.3%.
. United States v. Aluminum Co. of America, supra, 377 U.S. at 281, 84 S.Ct. 1283.
. Stanley relies on Tampa Electric Co. v. Nashville Coal Co., 365 U.S. 320, 81 S.Ct. 623, 5 L.Ed.2d 580 (1961) to support its assertion that 1% is a de minimis share of the market. Tampa was brought under § 3 of the Clayton Act, which forbids certain types of exclusive dealing contracts where the effect of such a contract may be substantially to lessen competition or tend to create a monopoly in any line of commerce. 15 U.S.C. § 14. Tampa and Nashville had entered into a requirements contract under which Nashville agreed to supply Tampa’s coal requirements for a period of twenty years. The District Court and the Court of Appeals held the contract invalid under § 3, and the Supreme Court reversed. The Court said: “ . . . the proportionate volume of the total relevant coal product as to which the challenged contract preempted competition, less than 1%, is, conservatively speaking, quite insubstantial. A more accurate figure, even assuming pre-emption to the extent of the maximum anticipated total requirements would be .77%.” 365 U.S., at 333, 81 S.Ct., at 631. Justices Black and Douglas dissented.
‘‘Stanley and our dissenting brother,” ignore the significance of the fact that Tampa Electric involved the validity of a contract under Clayton § 3, not § 7. The parameters of analysis in § 7 cases are not the same as in § 3 cases. Courts are cautioned to exercise greater care before upholding a merger under § 7 inasmuch as “integration by merger is more suspect than integration by contract, because of the greater permanence of the former.” United States v. Philadelphia National Bank, supra, 374 U.S., at 366, 83 S.Ct., at 1743. Furthermore, the Court in Tampa thought it necessary to distinguish Standard Fashion Company v. Magrane-Hous-ton Company, 258 U.S. 346, 42 S.Ct. 360, 66 L.Ed. 653 (1922), a prior § 3 case which had invalidated a two-year exclusive agency contract between Standard, a manufacturer and distributor of patterns, and Margane, a Boston retail dry goods store. Standard FasMons, the Court said, involved a market with a dominant seller and there was no evidence of any concentration in the Tampa product market. Because the instant
*508case calls into question the validity of a merger under § 7, not the legality of a contract under § 3, and because of the concentrated structure of the cabinet hardware market, we find Stanley’s reliance on Tampa Blectric misplaced.
Stanley has also cited to us, without discussion, several district court eases, which, it says, involved de minimis foreclosures. We have carefully considered these cases and find them inapposite.
. In fact, some scholars are of the view that any horizontal acquisition involving a firm with more than 20% of the relevant market — Amerock’s share is 22-24% — should be prima facie illegal. See K. ICaysen & D. Turner, supra, at 133. Stigler, Mergers and Preventive Antitrust, 104 U.Pa.L.Rev. 176, 182 (1955).
. The Commission found that it was reasonably probable that Stanley would have become increasingly more active in the residential cabinet hardware segment of the relevant market by way of internal expansion had expansion not been effected by merger. Stanley disputes this finding and says that top level Stanley management rejected the option of internal expansion in residential cabinet hardware. Instead, however, Stanley concedes that in January, 1965, approximately nine months prior to initial merger contacts between Stanley and Ameroek, it was decided that Stanley would expand its production of architectural cabinet hardware. Donald Davis, then Executive Vice-President and now President of Stanley, in testimony before the Trial Examiner, stated: “I was convinced that the best thing for the Hardware Division to do was to try to maximize their sales and profits in their existing product lines rather than spending their time and efforts looking for . . . new growth areas . . . ” And he asserted that Stanley had decided “to concentrate [its] efforts in the area where [it] had some strength, namely, architectural cabinet hardware . . . . ”
Whether we accept the Commission’s or Stanley’s view, once it is understood that the parties agreed that the cabinet hardware market as a whole is the relevant product market for this case, it is clear that Stanley had plans to become an even more significant competitor in the market. Therefore maintenance of its independence in the concentrated market, even as a 1% competitor, was of great importance in holding open the possibility of future deconcentration.
. In view of our decision in this case, we have no occasion to pass on the merits of the Commission’s “toe-hold theory” which would have declared this merger illegal for the reason that even if Stanley were permitted to expand in the market via acquisition, it should have purchased one of the lesser firms in the industry, and not the market leader. Stanley urges that the “toehold theory” was not raised in the complaint, never litigated at the hearing, nor considered by the Examiner. It contends therefore, that any judgment based on the “toehold theory” would be violative of Fifth Amendment Due Process, and Section 5 of the Administrative Procedure Act, 5 Ü.S.C. § 554. We agree that the “toehold theory” was not liti*509gated before the Examiner, and that the Commission was without authority to consider it. Cf. Bendix Corp. v. FTC, 450 F.2d 534 (6th Cir. 1971). Because the “toehold theory,” however, was an alternative basis of illegality, and since the actual competition case adequately established the finding of invalidity under tlie Clayton Act by substantial evidence, the Commission’s error worked no prejudice to Stanley.
Finally, Stanley contends that the Commission prejudged the facts of the case thereby denying petitioner its right to a fair hearing. We have given this charge the serious attention it deserves but find it to be without merit.