delivered the opinion of the Court.

Hanover Shoe, Inc. (hereafter Hanover) is a manufacturer of shoes and a customer of United Shoe Machinery Corporation (hereafter United), a manufacturer and distributor of shoe machinery. In 1954 this Court affirmed the judgment of the District Court for the District of Massachusetts, 110 F. Supp. 295 (1953), in favor of the United States in a civil action against United under § 4 of the Sherman Act, 26 Stat. 209, 15 U. S. C. § 4. United Shoe Machinery Corp. v. United States, 347 U. S. 521. In 1955, Hanover brought the present treble-damage action against United in the District Court for the Middle District of Pennsylvania. In 1965 the District Court rendered judgment for Hanover and awarded trebled damages, including interest, of $4,239,609, as well as $650,000 in counsel fees. 245 F. Supp. 258. On appeal, the Court of Appeals for the Third Circuit affirmed the finding of liability but disagreed with the District Court on certain questions relating to the damage award. 377 F. 2d 776 (1967). Both Hanover and United sought review of the Court of Appeals’ decision, and we granted both petitions. 389 U. S. 818 (1967).

I.

Hanover’s action against United alleged that United had monopolized the shoe machinery industry in violation of § 2 of the Sherman Act; that United’s practice of leasing and refusing to sell its more complicated and important shoe machinery had been an instrument of the unlawful monopolization; and that therefore Han*484over should recover from United the difference between what it paid United in shoe machine rentals and what it would have paid had United been willing during the relevant period to sell those machines.

Section 5 (a) of the Clayton Act, 38 Stat. 731, as amended, 69 Stat. 283, 15 U. S. C. § 16 (a), makes a final judgment or decree in any civil or criminal suit brought by the United States under the antitrust laws "prima facie evidence ... as to all matters respecting which said judgment or decree would be an estoppel as between the parties thereto . . ..” Relying on this provision, Hanover submitted the findings, opinion, and decree rendered by Judge Wyzanski in the Government’s case as evidence that United monopolized and that the practice of refusing to sell machines was an instrument of the monopolization. United does not contest that prima facie weight is to be given to the judgment in the Government’s case. It does, however, contend that Judge Wyzanski’s decision did not determine that the practice of leasing and refusing to sell was an instrument of monopolization. This claim, rejected by the courts below, is the threshold issue in No. 463. If the 1953 judgment is not prima facie evidence of the illegality of the practice from which Hanover’s asserted injury arose, then Hanover, having offered no other convincing evidence of illegality, should not have recovered at all.1

Both the District Court and the Court of Appeals concluded that the lease only policy had been held illegal in *485the Government’s suit. We find no error in that determination, It is true that § 4 of the decree2 on which United relies condemned only certain clauses in the standard lease and that nowhere in the decree was any other aspect of United’s leasing system expressly described or characterized as illegal monopolization. It is also arguable that § 5 of the decree, which required that United thenceforward not “offer for lease any machine type, unless it also offers such type for sale,” was included merely to insure an effective remedy to dissipate the accumulated consequences of United’s monopolization. We are not, however, limited to the decree in determining the extent of estoppel resulting from the judgment in the Government’s case. If by reference to the findings, opinion, and decree it is determined that an issue was actually adjudicated in an antitrust suit brought by the Government, the private plaintiff can treat the outcome of the Government’s case as prima facie evidence on that issue. See Emich Motors Corp. v. General Motors Corp., 340 U. S. 558, 566-569 (1951).

Section 5 of the decree would have been a justifiable remedy even if the practice it banned had not been instrumental in the monopolization of the market. But in our view the trial court’s findings and opinion put on firm ground the proposition that the Government’s case involved condemnation of the lease only system as such. In both its opinion with respect to violation and its opinion with respect to remedy, the court not only dealt with the objectionable clauses in the standard *486lease but also addressed itself to the consequences of only leasing machines and to the manner in which that practice related to the maintenance of United’s monopoly power.3 These portions of the court’s opinion are well supported by its findings of fact, which also estop United as against the Government and which therefore constitute prima facie evidence in this case. We have set out the relevant findings in an Appendix to this opinion. They are themselves sufficient to show that the lease only system played a significant role in United’s monopolization of the shoe machinery market. Those findings were not limited to the particular provisions of United’s *487leases. They dealt as well with United’s policy of leasing but not selling its important machines, with the advantages of that practice to United, and with its impact on potential and actual competition. When the applicable standard for determining monopolization under § 2 is applied to these facts, it must be concluded that the District Court and the Court of Appeals did not err in holding that United’s practice of leasing and refusing to sell its major machines was determined to be illegal monopolization in the Government’s case.4

II.

The District Court found that Hanover would have bought rather than leased from United had it been given the opportunity to do. so.5 The District Court determined that if United had sold its important machines, the cost to Hanover would have been less than the rental paid for leasing these same machines. This difference in cost, trebled, is the judgment awarded to Hanover in the District Court. United claims, however, that Hanover suffered no legally cognizable injury, contending *488that the illegal overcharge during the damage period was reflected in the price charged for shoes sold by Hanover to its customers and that Hanover, if it had bought machines at lower prices, would have charged less and made no more profit than it made by leasing. At the very least, United urges, the District Court should have determined on the evidence offered whether these contentions were correct. The Court of Appeals, like the District Court, rejected this assertion of the so-called “passing-on” defense, and we affirm that judgment.6

Section 4 of the Clayton Act, 38 Stat. 731, 15 U. S. C. § 15, provides that any person “who shall be injured *489in his business or property by reason of anything forbidden in the antitrust laws may sue therefor . . . and shall recover threefold the damages by him sustained . . . We think it sound to hold that when a buyer shows that the price paid by him for materials purchased for use in his business is illegally high and also shows the amount of the overcharge, he has made out a prima facie case of injury and damage within the meaning of § 4.

If in the face of the overcharge the buyer does nothing and absorbs the loss, he is entitled to treble damages. This much seems conceded. The reason is that he has paid more than he should and his property has been illegally diminished, for had the price paid been lower his profits would have been higher. It is also clear that if the buyer, responding to the illegal price, maintains his own price but takes steps to increase his volume or to decrease other costs, his right to damages is not destroyed. Though he may manage to maintain his profit level, he would have made more if his purchases from the defendant had cost him less. We hold that the buyer is equally entitled to damages if he raises the price for his own product. As long as the seller continues to charge the illegal price, he takes from the buyer more than the law allows. At whatever price the buyer sells, the price he pays the seller remains illegally high, and his profits would be greater were his costs lower.

Fundamentally, this is the view stated by Mr. Justice Holmes in Chattanooga Foundry & Pipe Works v. City of Atlanta, 203 U. S. 390 (1906), where Atlanta sued the defendants for treble damages for antitrust violations in connection with the city's purchases of pipe for its waterworks system. The Court affirmed a judgment in favor of the city for an amount measured by the difference between the price paid and what the market or fair price would have been had the sellers not com*490bined, the Court saying that the city “was injured in its property, at least, if not in its business of furnishing water, by being led to pay more than the worth of the pipe. A person whose property is diminished by a payment of money wrongfully induced is injured in his property.” Id,., at 396. The same approach was evident in Thomsen v. Cayser, 243 U. S. 66 (1917), another treble-damage antitrust case.7 With respect to overcharge cases arising under the transportation laws, similar views were expressed by Mr. Justice Holmes in Southern Pacific Co. v. Darnell-Taenzer Lumber Co., 245 U. S. 531, 533 (1918), and by Mr. Justice Brandeis in Adams v. Mills, 286 U. S. 397, 406-408 (1932). In those cases the possibility that -plaintiffs had recouped the overcharges from their customers was held irrelevant in assessing damages.8

*491United seeks to limit the general principle that the victim of an overcharge is damaged within the meaning of § 4 to the extent of that overcharge. The rule, United argues, should be subject to the defense that economic *492circumstances were such that the overcharged buyer could only charge his customers a higher price because the price to him was higher. It is argued that in such circumstances the buyer suffers no loss from the overcharge. This situation might be present, it is said, where the overcharge is imposed equally on all of a buyer’s competitors and where the demand for the buyer’s product is so inelastic that the buyer and his competitors could all increase their prices by the amount of the cost increase without suffering a consequent decline in sales.

We are not impressed with the argument that sound laws of economics require recognizing this defense. A wide range of factors influence a company’s pricing policies. Normally the impact of a single change in the relevant conditions cannot be measured after the fact; indeed a businessman may be unable to state whether, *493had one fact been different (a single supply less expensive, general economic conditions more buoyant, or the labor market tighter, for example), he would have chosen a different price. Equally difficult to determine, in the real economic world rather than an economist’s hypothetical model, is what effect a change in a company’s price will have on its total sales. Finally, costs per unit for a different volume of total sales are hard to estimate. Even if it could be shown that the buyer raised his price in response to, and in the amount of, the overcharge and that his margin of profit and total sales had not thereafter declined, there would remain the nearly insuperable difficulty of demonstrating that the particular plaintiff could not or would not have raised his prices absent the overcharge or maintained the higher price had the overcharge been discontinued. Since establishing the applicability of the passing-on defense would require a convincing showing of each of these virtually unascertainable figures, the task would normally prove insurmountable.9 On the other hand, it is not unlikely that if the existence of the defense is generally confirmed, antitrust defendants will frequently seek to establish its applicability. Treble-damage actions would often require additional long and complicated proceedings involving massive evidence and complicated theories.

*494In addition, if buyers are subjected to the passing-on defense, those who buy from them would also have to meet the challenge that they passed on the higher price to their customers. These ultimate consumers, in today's case the buyers of single pairs of shoes, would have only a tiny stake in a lawsuit and little interest in attempting a class action. In consequence, those who violate the antitrust laws by price fixing or monopolizing would retain the fruits of their illegality because no one was available who would bring suit against them. Treble-damage actions, the importance of which the Court has many times emphasized, would be substantially reduced in effectiveness.

Our conclusion is that Hanover proved injury and the amount of its damages for the purposes of its treble-damage suit when it proved that United had overcharged it during the damage period and showed the amount of the overcharge; United was not entitled to assert a passing-on defense. We recognize that there might be situations — for instance, when an overcharged buyer has a pre-existing “cost-plus” contract, thus making it easy to prove that he has not been damaged — where the considerations requiring that the passing-on defense not be permitted in this case would not be present. We also recognize that where no differential can be proved between the price unlawfully charged and some price that the seller was required by law to charge, establishing damages might require a showing of loss of profits to the buyer.10

*495III.

The District Court held that Hanover was entitled to damages for the period commencing July 1, 1939, and terminating September 21, 1955. The former date represented the greatest retrospective reach permitted under the applicable statute of limitations, and the latter date was that upon which Hanover filed its suit. In addition to somewhat shortening the forward' reach of the damage period,11 the Court of Appeals ruled that June 10, 1946, rather than July 1, 1939, marked the commencement of the damages period. June 10, 1946, was the date this Court decided American Tobacco Co. v. United States, 328 U. S. 781, which endorsed the views of the Court of Appeals for the Second Circuit in United States v. Aluminum Co. of America, 148 F. 2d 416 (1945). In the case before us the Court of Appeals concluded that the decisions in Alcoa-American Tobacco fundamentally altered the law of monopolization — that prior to them it was necessary to prove the existence of predatory practices as well as monopoly power, whereas afterwards proof of predatory practices was not essential. The Court of Appeals was also of the view that because in prior litigation United’s leases had escaped condemnation as predatory practices illegal under § 1, United’s conduct should not be held to have violated § 2 at any time prior to June 10, 1946. 377 F. 2d, at 790. This holding has been challenged, and we reverse it.

*496The theory of the Court of Appeals seems to have been that when a party has significantly relied upon a clear and established doctrine, and the retrospective application of a newly declared doctrine would upset that justifiable reliance to his substantial injury, considerations of justice and fairness require that the new rule apply prospectively only. Pointing to recent decisions of this Court in the area of the criminal law, the Court of Appeals could see no reason why the considerations which had favored only prospective application in those cases should not be applied as well as in the civil area, especially in a treble-damage action. There is, of course, no reason to confront this theory unless we have before us a situation in which there was a clearly declared judicial doctrine upon which United relied and under which its conduct was lawful, a doctrine which was overruled in favor of a new rule according to which conduct performed in reliance upon the old rule would have been unlawful. Because we do not believe that this case presents such a situation, we have no occasion to pass upon the theory of the Court of Appeals.

Neither the opinion in Alcoa nor the opinion in Amen-can Tobacco indicated that the issue involved was novel, that innovative principles were necessary to resolve it, or that the issue had been settled in prior cases in a manner contrary to the view held by those courts. In ruling that it was not necessary to exclude competitors to be guilty of monopolization, the Court of Appeals for the Second Circuit relied upon a long line of cases in this Court stretching back to 1912. 148 F. 2d, at 429. The conclusion that actions which will show monopolization are not “limited to manoeuvres not honestly industrial” was also premised on earlier opinions of this Court, particularly United States v. Swift & Co., 286 U. S. 106, 116 (1932). In the American Tobacco case, this Court noted *497that the precise question before it had not been previously decided, 328 U. S., at 811, and gave no indication that it thought it was adopting a radically new interpretation of the Sherman Act. Like the Court of Appeals, this Court relied for its conclusion upon existing authorities.12 These cases make it clear that there was no ac*498cepted interpretation of the Sherman Act which conditioned a finding of monopolization under § 2 upon a showing of predatory practices by the monopolist.13 In neither case was there such an abrupt and fundamental shift in doctrine as to constitute an entirely new rule which in effect replaced an older one. Whatever *499development in antitrust law was brought about was based to a great extent on existing authorities and was an extension of doctrines which had been growing and developing over the years. These cases did not constitute a sharp break in the line of earlier authority or an avulsive change which caused the current of the law thereafter to flow between new banks. We cannot say that prior to those cases potential antitrust defendants would have been justified in thinking that then current antitrust doctrines permitted them to do all acts conducive to the creation or maintenance of a monopoly, so long as they avoided direct exclusion of competitors or other predatory acts.14

United relies heavily on three Sherman Act cases brought against it or its predecessors by the United States and decided by this Court. United argues that these cases demonstrate both that before Alcoa-American Tobacco the law was substantially different and that its leasing practices had been deemed by this Court not to be instruments of monopolization. United States v. Winslow, 227 U. S. 202 (1913); United States v. United Shoe Machinery Co. of New Jersey, 247 U. S. 32 (1918); United Shoe Machinery Corp. v. United States, 258 U. S. 451 (1922). In our opinion, however, United overreads and exaggerates the significance of these three cases. In Winslow, the Government charged the three groups of companies which had merged to form United with a violation of § 1. The trial court construed the indictment to pertain only to the merger of the companies and not to business practices which resulted from the merger; most significantly, it excluded United’s leasing policies *500from consideration. The Court specifically stated that “[t]he validity of the leases or of a combination contemplating them cannot be passed upon in this case.” 227 U. S., at 217.

The third case, decided in 1922, was brought under § 3 of the Clayton Act rather than § 2 of the Sherman Act. This Court affirmed a decree enjoining United from making leases containing certain clauses, terms, and conditions. Nothing in that case indicates that predatory practices had to be shown to prove a § 2 monopoly charge or that the leases, or the clauses in them which were left undisturbed, would not adequately demonstrate monopolization by an enterprise with monopoly power.

Of the three cases, the 1918 case most strongly supports United. It involved a civil action by the United States charging violations of §§ 1 and 2 of the Sherman Act. The Government contended that United’s machinery leases and license agreements had been used to consummate both violations. A three-judge court dismissed the bill and this Court affirmed by a vote of 4 to 3. There is no question but that the leases as they were then constituted were held unassailable under § 1; the reasons for this ruling are not clear. As for the § 2 charge, we cannot read the opinion as specifying what course of conduct would amount to monopolization under § 2 if engaged in by a concern with monopoly power. At most the holding was that the leases themselves did not prove a § 2 charge — did not themselves prove monopoly power as well as monopolization. But the issue in the case before us now is not whether United’s leasing system proves monopoly power but whether, once monopoly power is shown, leasing the way United leased sufficiently shows an intent to exercise that power. There is little, if anything, in the 1918 opinion which is illuminating on this issue. Indeed, it may fairly be read as holding that United did not have monopoly power over the market at all, for in rejecting the claim that United’s practice of *501leasing was illegal when used by a corporation dominant in the market, the Court said:

“This, however, is assertion and relies for its foundation upon the assumption of an illegal dominance by the United Company that has been found not to exist. This element, therefore, must be put to one side and the leases regarded in and of themselves and by the incentives that induced their execution _” 247 U. S., at 60.

Any comfort United might have received from the 1918 case with respect to the legality of its leasing system when employed by one with monopoly power should have been short-lived. In the third case, which was brought under § 3 of the Clayton Act, and in which all the remaining Justices making up the majority in the 1918 case except Mr. Justice McKenna voted with the Court, the opinion for the Court described the 1918 decision as follows:

“That the leases were attacked under the former bill as violative of the Sherman Act is true, but they were sustained as valid and binding agreements within the rights of holders of patents.” 258 U. S., at 460.

This view was supported by other references to the 1918 opinion which described the question at issue there as being whether United's leases went beyond the exercise of a lawful monopoly.

One might possibly disagree with this reading of the 1918 opinion, but it was an authoritative gloss. After 1922 and after the expiration of the patents on its major machines, there was no sound basis to justify reliance by United on the 1918 case as a definitive pronouncement that its leasing system provided legally insufficient evidence of monopolization, once United’s power over the market was satisfactorily shown. The prior cases immunized United’s monopoly insofar as it originated *502in a merger of allegedly competing companies and perhaps are of some help to United in other respects. But they do not establish either that prior to 1946 there was a well-defined interpretation of the Sherman Act which was abruptly overruled in Alcoa-American Tobacco or that United’s leasing system could not be considered an instrument for the exercise and maintenance of monopoly power.

In these circumstances, there is no room for argument that Hanover’s damages should reach back only to the date of the American Tobacco decision. Having rejected the contention that Alcoa-American Tobacco changed the law of monopolization in a way which should be given only prospective effect, it follows that Hanover is entitled to damages for the entire period permitted by the applicable statute of limitations.15

I — f

Two questions are raised here about the manner m which damages were computed by the courts below. Hanover argues that the Court of Appeals erred in requiring the District Court, on remand, to take account of the additional taxes Hanover would have paid, had it purchased machines instead of renting them during the years in question. The Court of Appeals evidently *503felt that since only after-tax profits can be reinvested or distributed to shareholders, 'Hanover was damaged only to the extent of the after-tax profits that it failed to receive. The view of the Court of Appeals is sound in theory, but it overlooks the fact that in practice the Internal Revenue Service has taxed recoveries for tor-tious deprivation of profits at the time the recoveries are made, not by reopening the earlier years. See Commissioner v. Glenshaw Glass Co., 348 U. S. 426 (1955). As Hanover points out, since it will be taxed when it recovers damages from United for both the actual and the trebled damages, to diminish the actual damages by the amount of the taxes that it would have paid had it received greater profits in the years it was damaged would be to apply a double deduction for taxation, leaving Hanover with less income than it would have had if United had not injured it. It is true that accounting for taxes in the year when damages are received rather than the year when profits were lost can change the amount of taxes the Revenue Service collects; as United shows, actual rates of taxation were much higher in some of the years when Hanover was injured than they are today. But because the statute of limitations frequently will bar the Commissioner from recomputing for earlier years, and because of the policy underlying the statute of limitations — the fact that such recomputations are immensely difficult or impossible when a long period has intervened— the rough result of not taking account of taxes for the year of injury but then taxing recovery when received seems the most satisfactory outcome. The District Court therefore did not err on this question, and the Court of Appeals should not have required a recomputation.

United contends that if Hanover had bought machines instead of leasing them, it would have had to invest its own capital in the machines. United argues that the District Court erred in computing damages because it did not properly take account of the cost of capital to *504Hanover. The District Court found that in the years in question Hanover was able to borrow money for between 2% and 2.5% per annum, and that-had Hanover bought machines it would have obtained the necessary capital by borrowing at about this rate. It therefore deducted an interest component of 2.5% from the profits it thought Hanover would have earned by purchasing machines. Our review of the record convinces us that the courts below did not err in these determinations; on the basis of the determinations of fact, Hanover’s damages were properly computed.16

The judgment of the Court of Appeals is affirmed in part and reversed in part, and the cases are remanded for further proceedings consistent with this opinion.

It is so ordered.

APPENDIX TO OPINION OF THE COURT.

Excerpts From Judge Wyzanski’s Opinion in United States v. United Shoe Machinery Corp., 110 F. Supp. 295, 323-325 (D. Mass. 1953).

Effects of the Leasing System.

The effect of United’s leasing system as it works in practice may be examined from the viewpoints of United, of the shoe manufacturers, and of competitors potential or actual.

*505For United these are the advantages, (a) United has enjoyed a greater stability of annual revenues than is customary among manufacturers of other capital goods. But this is not due exclusively to the practice of leasing as distinguished from selling. It is attributable to the effects of leasing when, as is the case with United, the lessor already has a predominant share of the market, (b) United has been able to conduct research activities more favorably than if it sold its machines outright. The leasing system, especially the service aspect of that system, has given United constant access to shoe manufacturers and their problems. This has promoted United’s knowledge of their problems and has stimulated United’s shoe machinery development. This research knowledge would not be diminished substantially if United’s service activities covered fewer factories. But if all access to shoe factories were denied the diminution would be of great consequence to research, (c) The steadiness of revenues, attributable, as stated above, not to the leases alone, but to leases in a market dominated by the lessor, has tended to promote fairly steady appropriations to research. But these appropriations declined in the 1929 depression. Research expenditures might or might not be increased if competition were increased. The experience of United when faced with Compo’s cement process suggests that declining revenues, no less than steady revenues, may promote research expenditures, (d) United has kept its leased machines in the best possible condition. (e) Under the leasing system United has enjoyed a wide distribution of machinery in a relatively narrow market. But this is merely another way of saying that United’s market position, market power, lease provisions, and lease practices give it an advantage over competitors.

Upon shoe manufacturers, United’s leasing system has had these effects. It has been easy for a person with modest capital and of something less than superior effi*506ciency to become a shoe manufacturer. He can get machines without buying them; his machines are serviced without separate charges; he can conveniently exchange an older United model for a new United model; he can change from one process to another; and his costs of machinery per pair of shoes produced closely approximate the machinery costs of every other manufacturer using the same machinery to produce shoes by the same process. Largely as a consequence of these factors, there were in 1950, 1,300 factories each having a daily production capacity of 3,000 pairs a day or less; 100 factories each having a capacity of 3,000 to 8,000 pairs; and 40 larger manufacturers. Many of these larger manufacturers, who collectively account for 40% of the shoe production of the United States, started in a small way and flourished under United’s leasing system. Moreover the testimony in this case indicates virtually no shoe manufacturers who are dissatisfied with the present system. It cannot be said whether this absence of expressed dissatisfaction is due to lack of actual dissatisfaction, to practical men’s preference for what they regard as a fair system, even if it should be monopolistic, or to fear, inertia, or reluctance to testify.

However, while United’s system has made it easier to enter the shoe manufacturing industry than to enter many, perhaps most, other manufacturing industries, it has not necessarily promoted in the shoe manufacturing field the goals of a competitive economy and an open society. Without attempting to make findings that are more precise than the evidence warrants, this much can be definitely stated. If United shoe machinery were available upon a sale basis, then—

(a) Some shoe manufacturers would be able to secure credit whether by conditional sales, chattel mortgages, or other devices.

*507(b) Under such a system, there is no reason to suppose that a purchaser's first installment on a machine would significantly exceed the deposit now often required of a new shoe manufacturer by United.

(c) A few shoe manufacturers would be able to borrow at rates of interest comparable to the interest rates at which United borrows, or raises capital.

(d) Some shoe manufacturers would be able to provide for themselves service at a cost less than the average cost to United of supplying service to all lessees of its machines.

(e) Those manufacturers who bought United machines would not be subject, as are those manufacturers who lease United machines, to the unilateral decision of United whether or not to continue or modify those informal policies which are not written in the leases and to which United is not expressly committed for any specific future period. While there is no evidence that United plans any change in its informal policies, and while United has not heretofore proceeded to alter its informal policies on the basis of its approval or disapproval of individual manufacturers, United has not expressly committed itself to continue, for example, its 1935 plan for return of machines, its right of deduction fund, its waiver for 4 months of unit ■ charges, or its present high standard of service. United's reserved power with respect to these matters gives it some greater degree of psychological, and some greater degree of economic control, than a seller of machinery would have.

(f) Some manufacturers who had bought machinery would find that financial and psychological considerations made them more willing than lessees would be, to dispose of already acquired United machines and to take on competitors’ machines in their place.

In looking at United’s leasing system from the viewpoint of potential and actual competition, it must be *508confessed at the outset, that any system of selling or leasing one company’s machines will, of course, impede to some extent the distribution of another company’s machines. If a shoe manufacturer has already acquired one company’s machinery either by outright purchase, by conditional purchase, or on lease on any terms whatsoever, the existence of that machine in the factory is a possible impediment to the marketing of a competitive machine.

Yet as already noted, a shoe manufacturer may psychologically or economically be more impeded by a leasing than by a selling system. And this general observation is buttressed by a study of features in the United leasing system which have a special deterrent effect. Though these features are stated separately, and some of them alone are important impediments, they must be appraised collectively to appreciate the full deterrent effect.

(a) The 10 year term is a long commitment.

(b) A shoe manufacturer who already has a United leased machine which can perform all the available work of a particular type may be reluctant to experiment with a competitive machine to the extent he would wish. He may hesitate to ask for permission to avoid the full capacity clause. If permission is given for an experimental period he may find the experimental period too short. Thus a competitor may not get a chance to have his machine adequately tried out by a shoe manufacturer. If a shoe manufacturer prefers a competitive machine to a United machine on hand, he may not know the exact rate at which future payments may be commuted. If he knows, he may find that a fresh outlay to make those commuted payments (which admittedly are not solely for revenue but also are for protection against competition, and which admittedly discriminate in favor of a lessee who takes a new United machine and not a competitor’s machine) plus the rentals he has already *509paid cost him more than if he had bought a similar machine in the first place and were now to dispose of it in trade or in a second-hand market. Thus for a maker of competitive machines he may be a less likely customer than if United had initially allowed him to buy the machine.

(c) United’s lease system makes impossible a secondhand market in its own machines. This has two effects. It prevents United from suffering that kind of competition which a second-hand market offers. Also it prevents competitors from acquiring United machines with a view to copying such parts of the machines as are not patented, and with a view to experimenting with improvements without disclosing them to United.

(d) United’s practice of rendering repair service only on its own machines and without separate charge has brought about a situation in which there are almost no large scale independent repair companies. Hence when a typical small shoe manufacturer is considering whether to acquire a complicated shoe machine, he must look to the manufacturer of that machine for repair service. And a competitor of United could not readily market such a complicated machine unless in addition to offering the machine he was prepared to supply service. As the experience of foreign manufacturers indicates, this has proved to be a serious stumbling block to those who have sought to compete with United.

(e) If a shoe manufacturer is deciding whether to introduce competitive machines, (either for new operations or as replacements for United machines on which the lease has not expired), he faces the effect of those decisions upon his credit under the Right of Deduction Fund. If he already has virtually all United machines, and if he replaces few of them by competitive machines, the Fund will take care of substantially all his so-called deferred charges, and may cover some of his minimum payments. This is because credit to the Fund earned *510by a particular machine enures to the benefit of all leased machines in the factory, and the maximum advantage to the shoe manufacturer is to have a large number of United machines to which the credit can be applied. This advantage to the shoe manufacturer of acquiring and keeping a full line of United machines deters, though probably only mildly, the opportunities of a competing shoe manufacturer.

dissenting.

Hanover sued United under the Clayton Act for damages allegedly flowing from United's practice of offering its machines for lease but not for sale. Hanover did not attempt to prove as an original matter that this practice violated the antitrust laws. Instead, it relied exclusively upon § 5 (a) of the Clayton Act, 38 Stat. 731, as amended, which provides:

“A final judgment or decree heretofore or hereafter rendered in any civil or criminal proceeding brought by or on behalf of the United States under the antitrust laws to. the effect that a defendant has violated said laws shall be prima facie evidence against such defendant in any action or proceeding brought by any other party against such defendant under said laws ... as to all matters respecting which said judgment or decree would be an estoppel as between the parties thereto . . . .” 15 U. S. C. § 16(a).

Hanover recovered an award of treble damages solely upon the theory that the 1953 judgment and decree in United States v. United Shoe Machinery Corp., 110 F. Supp. 295, aff’d per curiam, 347 U. S. 521, had established the unlawfulness of United’s practice of making its machines available by lease only. So it follows, as the Court says, “[i]f the 1953 judgment is not prima facie evidence of the illegality of the practice from which *511Hanover’s asserted injury arose, then Hanover, having offered no other convincing evidence of illegality, should not have recovered at all.” Ante, at 484.

I think that the 1953 judgment did not have the broad effect the Court attributes to it today. On the contrary, that judgment, it seems evident to me, held unlawful only particular kinds of leases with particular provisions, not United’s general practice of leasing only.1

The only precedent cited by the Court for its expansive application of § 5 (a) is Emich Motors Corp. v. General Motors Corp., 340 U. S. 558. That case dealt with the estoppel effect of a general jury verdict in a criminal case. We deal here with a civil case which was tried to a federal judge, who rendered a thoroughly considered opinion and carefully precise decree.

One section of the decree, § 2, broadly set out what the court found United’s antitrust violations to be:

“Defendant violated § 2 of the Sherman Act, 15 U. S. C. A. § 2, by monopolizing the shoe machinery trade and commerce among the several States. Defendant violated the same section of the law by monopolizing that part of the interstate trade and commerce in tacks, nails, eyelets, grommets, and hooks, which is concerned with supplying the demand for those products by shoe factories within the United States. . . .” 110 F. Supp., at 352.

Another section of the decree, § 4, clearly specified the unlawful means by which these antitrust violations had been accomplished, and United’s general leasing practice was not oiie of those means:

“All leases made by defendant which include either a ten-year term, or a full capacity clause, or deferred *512payment charges, and all leases under which during the life of the leases defendant has rendered repair and other service without making them subject to separate, segregated charges, are declared to have been means whereby defendant monopolized the shoe machinery market.” Ibid.

In addition to these two sections setting forth the violations found, the decree contained some 20 remedial sections. Section 3 enjoined the violations found in § 2. Section 6 prohibited the particular types of leases found to be unlawful in § 4. Another section of the decree, § 5, went further and provided that in the future United’s machines must be offered for sale as well as for lease. But it is a commonplace that “relief, to be effective, must go beyond the narrow limits of the proven violation,” United States v. Gypsum Co., 340 U. S. 76, 90. United States v. Loew’s Inc., 371 U. S. 38, 53; United States v. Bausch & Lomb Co., 321 U. S. 707, 724.

1 can find nothing in Judge Wyzanski’s written opinion in the 1953 case to suggest that he found United’s lease-only practice, as such, to be a violation of the antitrust laws or illegal in any way.2 To the contrary, that opinion repeatedly emphasized the anticompetitive effects of the particular types of leases held illegal, and carefully explained that the purpose of requiring that customers *513in the future be given an option to purchase was to create an eventual second-hand market in United’s machines and to make the machines available to United’s competitors, so that they might study and copy them. 110 F. Supp., at 349-350. The opinion specifically stated that the reason for ordering United to offer its machines for sale was not to widen the choices available to customers.3

The Court today adds as an Appendix to its opinion— like a deus ex machina — Judge Wyzanski’s findings of fact. But it is irrelevant with respect to § 5 (a) that the 1953 findings describe United’s lease-only practice, when neither the decree nor the opinion held that practice to be unlawful.

The real key to why the Court has gone astray in this case is to be found, I think, in the concluding sentence of Part I of the Court’s opinion. For there the Court reveals that it is really not trying to determine what Judge Wyzanski decided in 1953, but is determining instead how this Court would decide the issues if the 1953 case were before it as an original matter today.4

In my view the 1953 United Shoe decision does not establish United’s liability to Hanover. I do not reach, therefore, the other questions dealt with in the Court’s opinion.

I would reverse the judgment of the Court of Appeals.