II. Monopolization

Section 2 of the Sherman Act makes it unlawful for a firm to "monopolize." 15 U.S.C. s 2. The offense of monopolization has two elements: "(1) the possession of monopoly power in the relevant market and (2) the willful acquisition or maintenance of that power as distinguished from growth or development as a consequence of a superior product, business acumen, or historic accident." United States v. Grinnell Corp., 384 U.S. 563, 570-71 (1966). The District Court applied this test and found that Microsoft possesses monopoly power in the market for Intel-compatible PC operating systems. Focusing primarily on Microsoft's efforts to suppress Netscape Navigator's threat to its operating system monopoly, the court also found that Microsoft maintained its power not through competition on the merits, but through unlawful means. Microsoft challenges both conclusions. We defer to the District Court's findings of fact, setting them aside only if clearly erroneous. Fed R. Civ. P. 52(a). We review legal questions de novo. United States ex rel. Modern Elec., Inc. v. Ideal Elec. Sec. Co., 81 F.3d 240, 244 (D.C. Cir. 1996).

We begin by considering whether Microsoft possesses monopoly power, see infra Section II.A, and finding that it does, we turn to the question whether it maintained this power through anticompetitive means. Agreeing with the District Court that the company behaved anticompetitively, see infra Section II.B, and that these actions contributed to the maintenance of its monopoly power, see infra Section II.C, we affirm the court's finding of liability for monopolization.

A. Monopoly Power

While merely possessing monopoly power is not itself an antitrust violation, see Northeastern Tel. Co. v. AT & T, 651 F.2d 76, 84-85 (2d Cir. 1981), it is a necessary element of a monopolization charge, see Grinnell, 384 U.S. at 570. The Supreme Court defines monopoly power as "the power to control prices or exclude competition." United States v. E.I. du Pont de Nemours & Co., 351 U.S. 377, 391 (1956). More precisely, a firm is a monopolist if it can profitably raise prices substantially above the competitive level. 2A Phillip E. Areeda et al., Antitrust Law p 501, at 85 (1995); cf. Ball Mem'l Hosp., Inc. v. Mut. Hosp. Ins., Inc., 784 F.2d 1325, 1335 (7th Cir. 1986) (defining market power as "the ability to cut back the market's total output and so raise price"). Where evidence indicates that a firm has in fact profitably done so, the existence of monopoly power is clear. See Rebel Oil Co. v. Atl. Richfield Co., 51 F.3d 1421, 1434 (9th Cir. 1995); see also FTC v. Indiana Fed'n of Dentists, 476 U.S. 447, 460-61 (1986) (using direct proof to show market power in Sherman Act s 1 unreasonable restraint of trade action). Because such direct proof is only rarely available, courts more typically examine market structure in search of circumstantial evidence of monopoly power. 2A Areeda et al., Antitrust Law p 531a, at 156; see also, e.g., Grinnell, 384 U.S. at 571. Under this structural approach, monopoly power may be inferred from a firm's possession of a dominant share of a relevant market that is protected by entry barriers. See Rebel Oil, 51 F.3d at 1434. "Entry barriers" are factors (such as certain regulatory requirements) that prevent new rivals from timely responding to an increase in price above the competitive level. See S. Pac. Communications Co. v. AT & T, 740 F.2d 980, 1001-02 (D.C. Cir. 1984).

The District Court considered these structural factors and concluded that Microsoft possesses monopoly power in a relevant market. Defining the market as Intel-compatible PC operating systems, the District Court found that Microsoft has a greater than 95% share. It also found the company's market position protected by a substantial entry barrier. Conclusions of Law, at 36.

Microsoft argues that the District Court incorrectly defined the relevant market. It also claims that there is no barrier to entry in that market. Alternatively, Microsoft argues that because the software industry is uniquely dynamic, direct proof, rather than circumstantial evidence, more appropriately indicates whether it possesses monopoly power. Rejecting each argument, we uphold the District Court's finding of monopoly power in its entirety.

1. Market Structure

a. Market definition

"Because the ability of consumers to turn to other suppliers restrains a firm from raising prices above the competitive level," Rothery Storage & Van Co. v. Atlas Van Lines, Inc., 792 F.2d 210, 218 (D.C. Cir. 1986), the relevant market must include all products "reasonably interchangeable by consumers for the same purposes." du Pont, 351 U.S. at 395. In this case, the District Court defined the market as "the licensing of all Intel-compatible PC operating systems worldwide," finding that there are "currently no products--and ... there are not likely to be any in the near future--that a significant percentage of computer users worldwide could substitute for [these operating systems] without incurring substantial costs." Conclusions of Law, at 36. Calling this market definition "far too narrow," Appellant's Opening Br. at 84, Microsoft argues that the District Court improperly excluded three types of products: non-Intel compatible operating systems (primarily Apple's Macintosh operating system, Mac OS), operating systems for non-PC devices (such as handheld computers and portal websites), and "middleware" products, which are not operating systems at all.

We begin with Mac OS. Microsoft's argument that Mac OS should have been included in the relevant market suffers from a flaw that infects many of the company's monopoly power claims: the company fails to challenge the District Court's factual findings, or to argue that these findings do not support the court's conclusions. The District Court found that consumers would not switch from Windows to Mac OS in response to a substantial price increase because of the costs of acquiring the new hardware needed to run Mac OS (an Apple computer and peripherals) and compatible software applications, as well as because of the effort involved in learning the new system and transferring files to its format. Findings of Fact p 20. The court also found the Apple system less appealing to consumers because it costs considerably more and supports fewer applications. Id. p 21. Microsoft responds only by saying: "the district court's market definition is so narrow that it excludes Apple's Mac OS, which has competed with Windows for years, simply because the Mac OS runs on a different microprocessor." Appellant's Opening Br. at 84. This general, conclusory statement falls far short of what is required to challenge findings as clearly erroneous. Pendleton v. Rumsfeld, 628 F.2d 102, 106 (D.C. Cir. 1980); see also Terry v. Reno, 101 F.3d 1412, 1415 (D.C. Cir. 1996) (holding that claims made but not argued in a brief are waived). Microsoft neither points to evidence contradicting the District Court's findings nor alleges that supporting record evidence is insufficient. And since Microsoft does not argue that even if we accept these findings, they do not support the District Court's conclusion, we have no basis for upsetting the court's decision to exclude Mac OS from the relevant market.

Microsoft's challenge to the District Court's exclusion of non-PC based competitors, such as information appliances (handheld devices, etc.) and portal websites that host server-based software applications, suffers from the same defect: the company fails to challenge the District Court's key factual findings. In particular, the District Court found that because information appliances fall far short of performing all of the functions of a PC, most consumers will buy them only as a supplement to their PCs. Findings of Fact p 23. The District Court also found that portal websites do not presently host enough applications to induce consumers to switch, nor are they likely to do so in the near future. Id. p 27. Again, because Microsoft does not argue that the District Court's findings do not support its conclusion that information appliances and portal websites are outside the relevant market, we adhere to that conclusion.

This brings us to Microsoft's main challenge to the District Court's market definition: the exclusion of middleware. Because of the importance of middleware to this case, we pause to explain what it is and how it relates to the issue before us.

Operating systems perform many functions, including allocating computer memory and controlling peripherals such as printers and keyboards. See Direct Testimony of Frederick Warren-Boulton p 20, reprinted in 5 J.A. at 3172-73. Operating systems also function as platforms for software applications. They do this by "exposing"--i.e., making available to software developers--routines or protocols that perform certain widely-used functions. These are known as Application Programming Interfaces, or "APIs." See Direct Testimony of James Barksdale p 70, reprinted in 5 J.A. at 2895-96. For example, Windows contains an API that enables users to draw a box on the screen. See Direct Testimony of Michael T. Devlin p 12, reprinted in 5 J.A. at 3525. Software developers wishing to include that function in an application need not duplicate it in their own code. Instead, they can "call"--i.e., use--the Windows API. See Direct Testimony of James Barksdale p p 70-71, reprinted in 5 J.A. at 2895-97. Windows contains thousands of APIs, controlling everything from data storage to font display. See Direct Testimony of Michael Devlin p 12, reprinted in 5 J.A. at 3525.

Every operating system has different APIs. Accordingly, a developer who writes an application for one operating system and wishes to sell the application to users of another must modify, or "port," the application to the second operat- ing system. Findings of Fact p 4. This process is both time-consuming and expensive. Id. p 30.

"Middleware" refers to software products that expose their own APIs. Id. p 28; Direct Testimony of Paul Maritz p p 234-36, reprinted in 6 J.A. at 3727-29. Because of this, a middleware product written for Windows could take over some or all of Windows's valuable platform functions--that is, developers might begin to rely upon APIs exposed by the middleware for basic routines rather than relying upon the API set included in Windows. If middleware were written for multiple operating systems, its impact could be even greater. The more developers could rely upon APIs exposed by such middleware, the less expensive porting to different operating systems would be. Ultimately, if developers could write applications relying exclusively on APIs exposed by middleware, their applications would run on any operating system on which the middleware was also present. See Direct Testimony of Avadis Tevanian, Jr. p 45, reprinted in 5 J.A. at 3113. Netscape Navigator and Java--both at issue in this case--are middleware products written for multiple operating systems. Findings of Fact p 28.

Microsoft argues that, because middleware could usurp the operating system's platform function and might eventually take over other operating system functions (for instance, by controlling peripherals), the District Court erred in excluding Navigator and Java from the relevant market. The District Court found, however, that neither Navigator, Java, nor any other middleware product could now, or would soon, expose enough APIs to serve as a platform for popular applications, much less take over all operating system functions. Id. p p 28-29. Again, Microsoft fails to challenge these findings, instead simply asserting middleware's "potential" as a competitor. Appellant's Opening Br. at 86. The test of reasonable interchangeability, however, required the District Court to consider only substitutes that constrain pricing in the reasonably foreseeable future, and only products that can enter the market in a relatively short time can perform this function. See Rothery, 792 F.2d at 218 ("Because the ability of consumers to turn to other suppliers restrains a firm from raising prices above the competitive level, the definition of the 'relevant market' rests on a determination of available substitutes."); see also Findings of Fact p 29 ("[I]t would take several years for middleware ... to evolve" into a product that can constrain operating system pricing.). Whatever middleware's ultimate potential, the District Court found that consumers could not now abandon their operating systems and switch to middleware in response to a sustained price for Windows above the competative level. Findings of Fact p p 28, 29. Nor is middleware likely to overtake the operating system as the primary platform for software development any time in the near future. Id.

Alternatively, Microsoft argues that the District Court should not have excluded middleware from the relevant market because the primary focus of the plaintiffs' s 2 charge is on Microsoft's attempts to suppress middleware's threat to its operating system monopoly. According to Microsoft, it is "contradict[ory]," 2/26/2001 Ct. Appeals Tr. at 20, to define the relevant market to exclude the "very competitive threats that gave rise" to the action. Appellant's Opening Br. at 84. The purported contradiction lies between plaintiffs' s 2 theory, under which Microsoft preserved its monopoly against middleware technologies that threatened to become viable substitutes for Windows, and its theory of the relevant market, under which middleware is not presently a viable substitute for Windows. Because middleware's threat is only nascent, however, no contradiction exists. Nothing in s 2 of the Sherman Act limits its prohibition to actions taken against threats that are already well-developed enough to serve as present substitutes. See infra Section II.C. Because market definition is meant to identify products "reasonably interchangeable by consumers," du Pont, 351 U.S. at 395, and because middleware is not now interchangeable with Windows, the District Court had good reason for excluding middleware from the relevant market.

b. Market power

Having thus properly defined the relevant market, the District Court found that Windows accounts for a greater than 95% share. Findings of Fact p 35. The court also found that even if Mac OS were included, Microsoft's share would exceed 80%. Id. Microsoft challenges neither finding, nor does it argue that such a market share is not predominant. Cf. Grinnell, 384 U.S. at 571 (87% is predominant); Eastman Kodak Co. v. Image Technical Servs., Inc., 504 U.S. 451, 481 (1992) (80%); du Pont, 351 U.S. at 379, 391 (75%).

Instead, Microsoft claims that even a predominant market share does not by itself indicate monopoly power. Although the "existence of [monopoly] power ordinarily may be inferred from the predominant share of the market," Grinnell, 384 U.S. at 571, we agree with Microsoft that because of the possibility of competition from new entrants, see Ball Mem'l Hosp., Inc., 784 F.2d at 1336, looking to current market share alone can be "misleading." Hunt-Wesson Foods, Inc. v. Ragu Foods, Inc., 627 F.2d 919, 924 (9th Cir. 1980); see also Ball Mem'l Hosp., Inc., 784 F.2d at 1336 ("Market share reflects current sales, but today's sales do not always indicate power over sales and price tomorrow.") In this case, however, the District Court was not misled. Considering the possibility of new rivals, the court focused not only on Micro- soft's present market share, but also on the structural barrier that protects the company's future position. Conclusions of Law, at 36. That barrier--the "applications barrier to entry"--stems from two characteristics of the software market: (1) most consumers prefer operating systems for which a large number of applications have already been written; and (2) most developers prefer to write for operating systems that already have a substantial consumer base. See Findings of Fact p p 30, 36. This "chicken-and-egg" situation ensures that applications will continue to be written for the already dominant Windows, which in turn ensures that consumers will continue to prefer it over other operating systems. Id.

Challenging the existence of the applications barrier to entry, Microsoft observes that software developers do write applications for other operating systems, pointing out that at its peak IBM's OS/2 supported approximately 2,500 applications. Id. p 46. This misses the point. That some developers write applications for other operating systems is not at all inconsistent with the finding that the applications barrier to entry discourages many from writing for these less popular platforms. Indeed, the District Court found that IBM's difficulty in attracting a larger number of software developers to write for its platform seriously impeded OS/2's success. Id. p 46.

Microsoft does not dispute that Windows supports many more applications than any other operating system. It argues instead that "[i]t defies common sense" to suggest that an operating system must support as many applications as Windows does (more than 70,000, according to the District Court, id. p 40) to be competitive. Appellant's Opening Br. at 96. Consumers, Microsoft points out, can only use a very small percentage of these applications. Id. As the District Court explained, however, the applications barrier to entry gives consumers reason to prefer the dominant operating system even if they have no need to use all applications written for it:

The consumer wants an operating system that runs not only types of applications that he knows he will want to use, but also those types in which he might develop an interest later. Also, the consumer knows that if he chooses an operating system with enough demand to support multiple applications in each product category, he will be less likely to find himself straitened later by having to use an application whose features disappoint him. Finally, the average user knows that, generally speaking, applications improve through successive versions. He thus wants an operating system for which successive generations of his favorite applications will be released--promptly at that. The fact that a vastly larger number of applications are written for Windows than for other PC operating systems attracts consumers to Windows, because it reassures them that their interests will be met as long as they use Microsoft's product.

Findings of Fact p 37. Thus, despite the limited success of its rivals, Microsoft benefits from the applications barrier to entry.

Of course, were middleware to succeed, it would erode the applications barrier to entry. Because applications written for multiple operating systems could run on any operating system on which the middleware product was present with little, if any, porting, the operating system market would become competitive. Id. p p 29, 72. But as the District Court found, middleware will not expose a sufficient number of APIs to erode the applications barrier to entry in the foreseeable future. See id. p p 28-29.

Microsoft next argues that the applications barrier to entry is not an entry barrier at all, but a reflection of Windows' popularity. It is certainly true that Windows may have gained its initial dominance in the operating system market competitively--through superior foresight or quality. But this case is not about Microsoft's initial acquisition of monopoly power. It is about Microsoft's efforts to maintain this position through means other than competition on the merits. Because the applications barrier to entry protects a dominant operating system irrespective of quality, it gives Microsoft power to stave off even superior new rivals. The barrier is thus a characteristic of the operating system market, not of Microsoft's popularity, or, as asserted by a Microsoft witness, the company's efficiency. See Direct Testimony of Richard Schmalensee p 115, reprinted in 25 J.A. at 16153-14.

Finally, Microsoft argues that the District Court should not have considered the applications barrier to entry because it reflects not a cost borne disproportionately by new entrants, but one borne by all participants in the operating system market. According to Microsoft, it had to make major investments to convince software developers to write for its new operating system, and it continues to "evangelize" the Windows platform today. Whether costs borne by all market participants should be considered entry barriers is the subject of much debate. Compare 2A Areeda & Hovenkamp, Antitrust Law s 420c, at 61 (arguing that these costs are entry barriers), and Joe S. Bain, Barriers to New Competition: Their Character and Consequences in Manufacturing Industries 6-7 (1956) (considering these costs entry barriers), with L.A. Land Co. v. Brunswick Corp., 6 F.3d 1422, 1428 (9th Cir. 1993) (evaluating cost based on "[t]he disadvantage of new entrants as compared to incumbents"), and George Stigler, The Organization of Industry 67 (1968) (excluding these costs). We need not resolve this issue, however, for even under the more narrow definition it is clear that there are barriers. When Microsoft entered the operating system market with MS-DOS and the first version of Windows, it did not confront a dominant rival operating system with as massive an installed base and as vast an existing array of applications as the Windows operating systems have since enjoyed. Findings of Fact p p 6, 7, 43. Moreover, when Microsoft introduced Windows 95 and 98, it was able to bypass the applications barrier to entry that protected the incumbent Windows by including APIs from the earlier ver- sion in the new operating systems. See id. p 44. This made porting existing Windows applications to the new version of Windows much less costly than porting them to the operating systems of other entrants who could not freely include APIs from the incumbent Windows with their own.

2. Direct Proof

Having sustained the District Court's conclusion that circumstantial evidence proves that Microsoft possesses monopoly power, we turn to Microsoft's alternative argument that it does not behave like a monopolist. Claiming that software competition is uniquely "dynamic," Appellant's Opening Br. at 84 (quoting Findings of Fact p 59), the company suggests a new rule: that monopoly power in the software industry should be proven directly, that is, by examining a company's actual behavior to determine if it reveals the existence of monopoly power. According to Microsoft, not only does no such proof of its power exist, but record evidence demonstrates the absence of monopoly power. The company claims that it invests heavily in research and development, id. at 88-89 (citing Direct Testimony of Paul Maritz p 155, reprinted in 6 J.A. at 3698 (testifying that Microsoft invests approximately 17% of its revenue in R&D)), and charges a low price for Windows (a small percentage of the price of an Intel- compatible PC system and less than the price of its rivals, id. at 90 (citing Findings of Fact p p 19, 21, 46)).

Microsoft's argument fails because, even assuming that the software market is uniquely dynamic in the long term, the District Court correctly applied the structural approach to determine if the company faces competition in the short term. Structural market power analyses are meant to determine whether potential substitutes constrain a firm's ability to raise prices above the competitive level; only threats that are likely to materialize in the relatively near future perform this function to any significant degree. Rothery, 792 F.2d at 218 (quoting Lawrence Sullivan, Antitrust s 12, at 41 (1977)) (only substitutes that can enter the market "promptly" should be considered). The District Court expressly considered and rejected Microsoft's claims that innovations such as handheld devices and portal websites would soon expand the relevant market beyond Intel-compatible PC operating systems. Because the company does not challenge these findings, we have no reason to believe that prompt substitutes are available. The structural approach, as applied by the District Court, is thus capable of fulfilling its purpose even in a changing market. Microsoft cites no case, nor are we aware of one, requiring direct evidence to show monopoly power in any market. We decline to adopt such a rule now.

Even if we were to require direct proof, moreover, Microsoft's behavior may well be sufficient to show the existence of monopoly power. Certainly, none of the conduct Microsoft points to--its investment in R&D and the relatively low price of Windows--is inconsistent with the possession of such power. Conclusions of Law, at 37. The R&D expenditures Microsoft points to are not simply for Windows, but for its entire company, which most likely does not possess a monopoly for all of its products. Moreover, because innovation can increase an already dominant market share and further delay the emergence of competition, even monopolists have reason to invest in R&D. Findings of Fact p 61. Microsoft's pricing behavior is similarly equivocal. The company claims only that it never charged the short-term profit-maximizing price for Windows. Faced with conflicting expert testimony, the District Court found that it could not accurately determine what this price would be. Id. p 65. In any event, the court found, a price lower than the short-term profit-maximizing price is not inconsistent with possession or improper use of monopoly power. Id. p p 65-66. Cf. Berkey Photo, Inc. v. Eastman Kodak Co., 603 F.2d 263, 274 (2d Cir. 1979) ("[I]f monopoly power has been acquired or maintained through improper means, the fact that the power has not been used to extract [a monopoly price] provides no succor to the monopolist."). Microsoft never claims that it did not charge the long-term monopoly price. Microsoft does argue that the price of Windows is a fraction of the price of an Intel-compatible PC system and lower than that of rival operating systems, but these facts are not inconsistent with the District Court's finding that Microsoft has monopoly power. See Findings of Fact p 36 ("Intel-compatible PC operating systems other than Windows [would not] attract[ ] significant demand ... even if Microsoft held its prices substantially above the competitive level.").

More telling, the District Court found that some aspects of Microsoft's behavior are difficult to explain unless Windows is a monopoly product. For instance, according to the District Court, the company set the price of Windows without considering rivals' prices, Findings of Fact p 62, something a firm without a monopoly would have been unable to do. The District Court also found that Microsoft's pattern of exclusionary conduct could only be rational "if the firm knew that it possessed monopoly power." Conclusions of Law, at 37. It is to that conduct that we now turn.

B. Anticompetitive Conduct

As discussed above, having a monopoly does not by itself violate s 2. A firm violates s 2 only when it acquires or maintains, or attempts to acquire or maintain, a monopoly by engaging in exclusionary conduct "as distinguished from growth or development as a consequence of a superior product, business acumen, or historic accident." Grinnell, 384 U.S. at 571; see also United States v. Aluminum Co. of Am., 148 F.2d 416, 430 (2d Cir. 1945) (Hand, J.) ("The successful competitor, having been urged to compete, must not be turned upon when he wins.").

In this case, after concluding that Microsoft had monopoly power, the District Court held that Microsoft had violated s 2 by engaging in a variety of exclusionary acts (not including predatory pricing), to maintain its monopoly by preventing the effective distribution and use of products that might threaten that monopoly. Specifically, the District Court held Microsoft liable for: (1) the way in which it integrated IE into Windows; (2) its various dealings with Original Equipment Manufacturers ("OEMs"), Internet Access Providers ("IAPs"), Internet Content Providers ("ICPs"), Independent Software Vendors ("ISVs"), and Apple Computer; (3) its efforts to contain and to subvert Java technologies; and (4) its course of conduct as a whole. Upon appeal, Microsoft argues that it did not engage in any exclusionary conduct.

Whether any particular act of a monopolist is exclusionary, rather than merely a form of vigorous competition, can be difficult to discern: the means of illicit exclusion, like the means of legitimate competition, are myriad. The challenge for an antitrust court lies in stating a general rule for distinguishing between exclusionary acts, which reduce social welfare, and competitive acts, which increase it.

From a century of case law on monopolization under s 2, however, several principles do emerge. First, to be condemned as exclusionary, a monopolist's act must have an "anticompetitive effect." That is, it must harm the competitive process and thereby harm consumers. In contrast, harm to one or more competitors will not suffice. "The [Sherman Act] directs itself not against conduct which is competitive, even severely so, but against conduct which unfairly tends to destroy competition itself." Spectrum Sports, Inc. v. McQuillan, 506 U.S. 447, 458 (1993); see also Brooke Group Ltd. v. Brown & Williamson Tobacco Corp., 509 U.S. 209, 225 (1993) ("Even an act of pure malice by one business competitor against another does not, without more, state a claim under the federal antitrust laws....").

Second, the plaintiff, on whom the burden of proof of course rests, see, e.g., Monsanto Co. v. Spray-Rite Serv. Corp., 465 U.S. 752, 763 (1984); see also United States v. Arnold, Schwinn & Co., 388 U.S. 365, 374 n.5 (1967), overruled on other grounds, Cont'l T.V., Inc. v. GTE Sylvania Inc., 433 U.S. 36 (1977), must demonstrate that the monopolist's conduct indeed has the requisite anticompetitive effect. See generally Brooke Group, 509 U.S. at 225-26. In a case brought by a private plaintiff, the plaintiff must show that its injury is "of 'the type that the statute was intended to forestall,' " Brunswick Corp. v. Pueblo Bowl-O-Mat, Inc., 429 U.S. 477, 487-88 (1977) (quoting Wyandotte Transp. v. United States, 389 U.S. 191, 202 (1967)); no less in a case brought by the Government, it must demonstrate that the monopolist's conduct harmed competition, not just a competitor.

Third, if a plaintiff successfully establishes a prima facie case under s 2 by demonstrating anticompetitive effect, then the monopolist may proffer a "procompetitive justification" for its conduct. See Eastman Kodak, 504 U.S. at 483. If the monopolist asserts a procompetitive justification--a nonpretextual claim that its conduct is indeed a form of competition on the merits because it involves, for example, greater efficiency or enhanced consumer appeal--then the burden shifts back to the plaintiff to rebut that claim. Cf. Capital Imaging Assocs., P.C. v. Mohawk Valley Med. Assocs., Inc., 996 F.2d 537, 543 (2d Cir. 1993).

Fourth, if the monopolist's procompetitive justification stands unrebutted, then the plaintiff must demonstrate that the anticompetitive harm of the conduct outweighs the procompetitive benefit. In cases arising under s 1 of the Sherman Act, the courts routinely apply a similar balancing approach under the rubric of the "rule of reason." The source of the rule of reason is Standard Oil Co. v. United States, 221 U.S. 1 (1911), in which the Supreme Court used that term to describe the proper inquiry under both sections of the Act. See id. at 61-62 ("[W]hen the second section [of the Sherman Act] is thus harmonized with ... the first, it becomes obvious that the criteria to be resorted to in any given case for the purpose of ascertaining whether violations of the section have been committed, is the rule of reason guided by the established law...."). As the Fifth Circuit more recently explained, "[i]t is clear ... that the analysis under section 2 is similar to that under section 1 regardless whether the rule of reason label is applied...." Mid-Texas Communications Sys., Inc. v. AT & T, 615 F.2d 1372, 1389 n.13 (5th Cir. 1980) (citing Byars v. Bluff City News Co., 609 F.2d 843, 860 (6th Cir. 1979)); see also Cal. Computer Prods., Inc. v. IBM Corp., 613 F.2d 727, 737 (9th Cir. 1979).

Finally, in considering whether the monopolist's conduct on balance harms competition and is therefore condemned as exclusionary for purposes of s 2, our focus is upon the effect of that conduct, not upon the intent behind it. Evidence of the intent behind the conduct of a monopolist is relevant only to the extent it helps us understand the likely effect of the monopolist's conduct. See, e.g., Chicago Bd. of Trade v. United States, 246 U.S. 231, 238 (1918) ("knowledge of intent may help the court to interpret facts and to predict consequences"); Aspen Skiing Co. v. Aspen Highlands Skiing Corp., 472 U.S. 585, 603 (1985).

With these principles in mind, we now consider Microsoft's objections to the District Court's holding that Microsoft violated s 2 of the Sherman Act in a variety of ways.

1. Licenses Issued to Original Equipment Manufacturers

The District Court condemned a number of provisions in Microsoft's agreements licensing Windows to OEMs, because it found that Microsoft's imposition of those provisions (like many of Microsoft's other actions at issue in this case) serves to reduce usage share of Netscape's browser and, hence, protect Microsoft's operating system monopoly. The reason market share in the browser market affects market power in the operating system market is complex, and warrants some explanation.

Browser usage share is important because, as we explained in Section II.A above, a browser (or any middleware product, for that matter) must have a critical mass of users in order to attract software developers to write applications relying upon the APIs it exposes, and away from the APIs exposed by Windows. Applications written to a particular browser's APIs, however, would run on any computer with that browser, regardless of the underlying operating system. "The overwhelming majority of consumers will only use a PC operating system for which there already exists a large and varied set of ... applications, and for which it seems relatively certain that new types of applications and new versions of existing applications will continue to be marketed...." Findings of Fact p 30. If a consumer could have access to the applications he desired--regardless of the operating sys- tem he uses--simply by installing a particular browser on his computer, then he would no longer feel compelled to select Windows in order to have access to those applications; he could select an operating system other than Windows based solely upon its quality and price. In other words, the market for operating systems would be competitive.

Therefore, Microsoft's efforts to gain market share in one market (browsers) served to meet the threat to Microsoft's monopoly in another market (operating systems) by keeping rival browsers from gaining the critical mass of users necessary to attract developer attention away from Windows as the platform for software development. Plaintiffs also argue that Microsoft's actions injured competition in the browser market--an argument we will examine below in relation to their specific claims that Microsoft attempted to monopolize the browser market and unlawfully tied its browser to its operating system so as to foreclose competition in the browser market. In evaluating the s 2 monopoly maintenance claim, however, our immediate concern is with the anticompetitive effect of Microsoft's conduct in preserving its monopoly in the operating system market.

In evaluating the restrictions in Microsoft's agreements licensing Windows to OEMs, we first consider whether plain- tiffs have made out a prima facie case by demonstrating that the restrictions have an anticompetitive effect. In the next subsection, we conclude that plaintiffs have met this burden as to all the restrictions. We then consider Microsoft's proffered justifications for the restrictions and, for the most part, hold those justifications insufficient.

a. Anticompetitive effect of the license restrictions

The restrictions Microsoft places upon Original Equipment Manufacturers are of particular importance in determining browser usage share because having an OEM pre-install a browser on a computer is one of the two most cost-effective methods by far of distributing browsing software. (The other is bundling the browser with internet access software distributed by an IAP.) Findings of Fact p 145. The District Court found that the restrictions Microsoft imposed in licensing Windows to OEMs prevented many OEMs from distributing browsers other than IE. Conclusions of Law, at 39-40. In particular, the District Court condemned the license provisions prohibiting the OEMs from: (1) removing any desktop icons, folders, or "Start" menu entries; (2) altering the initial boot sequence; and (3) otherwise altering the appearance of the Windows desktop. Findings of Fact p 213.

The District Court concluded that the first license restriction--the prohibition upon the removal of desktop icons, folders, and Start menu entries--thwarts the distribution of a rival browser by preventing OEMs from removing visible means of user access to IE. Id. p 203. The OEMs cannot practically install a second browser in addition to IE, the court found, in part because "[p]re-installing more than one product in a given category ... can significantly increase an OEM's support costs, for the redundancy can lead to confusion among novice users." Id. p 159; see also id. p 217. That is, a certain number of novice computer users, seeing two browser icons, will wonder which to use when and will call the OEM's support line. Support calls are extremely expensive and, in the highly competitive original equipment market, firms have a strong incentive to minimize costs. Id. p 210.

Microsoft denies the "consumer confusion" story; it observes that some OEMs do install multiple browsers and that executives from two OEMs that do so denied any knowledge of consumers being confused by multiple icons. See 11/5/98 pm Tr. at 41-42 (trial testimony of Avadis Tevanian of Apple), reprinted in 9 J.A. at 5493-94; 11/18/99 am Tr. at 69 (trial testimony of John Soyring of IBM), reprinted in 10 J.A. at 6222.

Other testimony, however, supports the District Court's finding that fear of such confusion deters many OEMs from pre-installing multiple browsers. See, e.g., 01/13/99 pm Tr. at 614-15 (deposition of Microsoft's Gayle McClain played to the court) (explaining that redundancy of icons may be confusing to end users); 02/18/99 pm Tr. at 46-47 (trial testimony of John Rose of Compaq), reprinted in 21 J.A. at 14237-38 (same); 11/17/98 am Tr. at 68 (deposition of John Kies of Packard Bell-NEC played to the court), reprinted in 9 J.A. at 6016 (same); 11/17/98 am Tr. at 67-72 (trial testimony of Glenn Weadock), reprinted in 9 J.A. at 6015-20 (same). Most telling, in presentations to OEMs, Microsoft itself represented that having only one icon in a particular category would be "less confusing for endusers." See Government's Trial Exhibit ("GX") 319 at MS98 0109453. Accordingly, we reject Microsoft's argument that we should vacate the District Court's Finding of Fact 159 as it relates to consumer confusion.

As noted above, the OEM channel is one of the two primary channels for distribution of browsers. By preventing OEMs from removing visible means of user access to IE, the license restriction prevents many OEMs from pre-installing a rival browser and, therefore, protects Microsoft's monopoly from the competition that middleware might otherwise present. Therefore, we conclude that the license restriction at issue is anticompetitive. We defer for the moment the question whether that anticompetitive effect is outweighed by Microsoft's proffered justifications.

The second license provision at issue prohibits OEMs from modifying the initial boot sequence--the process that occurs the first time a consumer turns on the computer. Prior to the imposition of that restriction, "among the programs that many OEMs inserted into the boot sequence were Internet sign-up procedures that encouraged users to choose from a list of IAPs assembled by the OEM." Findings of Fact p 210. Microsoft's prohibition on any alteration of the boot sequence thus prevents OEMs from using that process to promote the services of IAPs, many of which--at least at the time Microsoft imposed the restriction--used Navigator rather than IE in their internet access software. See id. p 212; GX 295, reprinted in 12 J.A. at 14533 (Upon learning of OEM practices including boot sequence modification, Microsoft's Chairman, Bill Gates, wrote: "Apparently a lot of OEMs are bundling non-Microsoft browsers and coming up with offerings together with [IAPs] that get displayed on their machines in a FAR more prominent way than MSN or our Internet browser."). Microsoft does not deny that the prohibition on modifying the boot sequence has the effect of decreasing competition against IE by preventing OEMs from promoting rivals' browsers. Because this prohibition has a substantial effect in protecting Microsoft's market power, and does so through a means other than competition on the merits, it is anticompetitive. Again the question whether the provision is nonetheless justified awaits later treatment.

Finally, Microsoft imposes several additional provisions that, like the prohibition on removal of icons, prevent OEMs from making various alterations to the desktop: Microsoft prohibits OEMs from causing any user interface other than the Windows desktop to launch automatically, from adding icons or folders different in size or shape from those supplied by Microsoft, and from using the "Active Desktop" feature to promote third-party brands. These restrictions impose significant costs upon the OEMs; prior to Microsoft's prohibiting the practice, many OEMs would change the appearance of the desktop in ways they found beneficial. See, e.g., Findings of Fact p 214; GX 309, reprinted in 22 J.A. at 14551 (March 1997 letter from Hewlett-Packard to Microsoft: "We are responsible for the cost of technical support of our customers, including the 33% of calls we get related to the lack of quality or confusion generated by your product.... We must have more ability to decide how our system is presented to our end users. If we had a choice of another supplier, based on your actions in this area, I assure you [that you] would not be our supplier of choice.").

The dissatisfaction of the OEM customers does not, of course, mean the restrictions are anticompetitive. The anti-competitive effect of the license restrictions is, as Microsoft itself recognizes, that OEMs are not able to promote rival browsers, which keeps developers focused upon the APIs in Windows. Findings of Fact p 212 (quoting Microsoft's Gates as writing, "[w]inning Internet browser share is a very very important goal for us," and emphasizing the need to prevent OEMs from promoting both rival browsers and IAPs that might use rivals' browsers); see also 01/13/99 Tr. at 305-06 (excerpts from deposition of James Von Holle of Gateway) (prior to restriction Gateway had pre-installed non-IE internet registration icon that was larger than other desktop icons). This kind of promotion is not a zero-sum game; but for the restrictions in their licenses to use Windows, OEMs could promote multiple IAPs and browsers. By preventing the OEMs from doing so, this type of license restriction, like the first two restrictions, is anticompetitive: Microsoft reduced rival browsers' usage share not by improving its own product but, rather, by preventing OEMs from taking actions that could increase rivals' share of usage.

b. Microsoft's justifications for the license restrictions

Microsoft argues that the license restrictions are legally justified because, in imposing them, Microsoft is simply "exercising its rights as the holder of valid copyrights." Appellant's Opening Br. at 102. Microsoft also argues that the licenses "do not unduly restrict the opportunities of Netscape to distribute Navigator in any event." Id.

Microsoft's primary copyright argument borders upon the frivolous. The company claims an absolute and unfettered right to use its intellectual property as it wishes: "[I]f intellectual property rights have been lawfully acquired," it says, then "their subsequent exercise cannot give rise to antitrust liability." Appellant's Opening Br. at 105. That is no more correct than the proposition that use of one's personal property, such as a baseball bat, cannot give rise to tort liability. As the Federal Circuit succinctly stated: "Intellectual property rights do not confer a privilege to violate the antitrust laws." In re Indep. Serv. Orgs. Antitrust Litig., 203 F.3d 1322, 1325 (Fed. Cir. 2000).

Although Microsoft never overtly retreats from its bold and incorrect position on the law, it also makes two arguments to the effect that it is not exercising its copyright in an unreasonable manner, despite the anticompetitive consequences of the license restrictions discussed above. In the first variation upon its unqualified copyright defense, Microsoft cites two cases indicating that a copyright holder may limit a licensee's ability to engage in significant and deleterious alterations of a copyrighted work. See Gilliam v. ABC, 538 F.2d 14, 21 (2d Cir. 1976); WGN Cont'l Broad. Co. v. United Video, Inc., 693 F.2d 622, 625 (7th Cir. 1982). The relevance of those two cases for the present one is limited, however, both because those cases involved substantial alterations of a copyrighted work, see Gilliam, 538 F.2d at 18, and because in neither case was there any claim that the copyright holder was, in asserting its rights, violating the antitrust laws, see WGN Cont'l Broad., 693 F.2d at 626; see also Cmty. for Creative Non-Violence v. Reid, 846 F.2d 1485, 1498 (D.C. Cir. 1988) (noting, again in a context free of any antitrust concern, that "an author [ ] may have rights against" a licensee that "excessively mutilated or altered" the copyrighted work).

The only license restriction Microsoft seriously defends as necessary to prevent a "substantial alteration" of its copyrighted work is the prohibition on OEMs automatically launching a substitute user interface upon completion of the boot process. See Findings of Fact p 211 ("[A] few large OEMs developed programs that ran automatically at the conclusion of a new PC system's first boot sequence. These programs replaced the Windows desktop either with a user interface designed by the OEM or with Navigator's user interface."). We agree that a shell that automatically prevents the Windows desktop from ever being seen by the user is a drastic alteration of Microsoft's copyrighted work, and outweighs the marginal anticompetitive effect of prohibiting the OEMs from substituting a different interface automatically upon completion of the initial boot process. We therefore hold that this particular restriction is not an exclusionary practice that violates s 2 of the Sherman Act.

In a second variation upon its copyright defense, Microsoft argues that the license restrictions merely prevent OEMs from taking actions that would reduce substantially the value of Microsoft's copyrighted work: that is, Microsoft claims each license restriction in question is necessary to prevent OEMs from so altering Windows as to undermine "the principal value of Windows as a stable and consistent platform that supports a broad range of applications and that is familiar to users." Appellant's Opening Br. at 102. Microsoft, however, never substantiates this claim, and, because an OEM's altering the appearance of the desktop or promoting programs in the boot sequence does not affect the code already in the product, the practice does not self-evidently affect either the "stability" or the "consistency" of the platform. See Conclusions of Law, at 41; Findings of Fact p 227. Microsoft cites only one item of evidence in support of its claim that the OEMs' alterations were decreasing the value of Windows. Defendant's Trial Exhibit ("DX") 2395 at MSV0009378A, reprinted in 19 J.A. at 12575. That document, prepared by Microsoft itself, states: "there are quality issues created by OEMs who are too liberal with the pre-install process," referring to the OEMs' installation of Windows and additional software on their PCs, which the document says may result in "user concerns and confusion." To the extent the OEMs' modifications cause consumer confusion, of course, the OEMs bear the additional support costs. See Findings of Fact p 159. Therefore, we conclude Microsoft has not shown that the OEMs' liberality reduces the value of Windows except in the sense that their promotion of rival browsers undermines Microsoft's monopoly--and that is not a permissible justification for the license restrictions.

Apart from copyright, Microsoft raises one other defense of the OEM license agreements: It argues that, despite the restrictions in the OEM license, Netscape is not completely blocked from distributing its product. That claim is insufficient to shield Microsoft from liability for those restrictions because, although Microsoft did not bar its rivals from all means of distribution, it did bar them from the cost-efficient ones.

In sum, we hold that with the exception of the one restriction prohibiting automatically launched alternative interfaces, all the OEM license restrictions at issue represent uses of Microsoft's market power to protect its monopoly, unredeemed by any legitimate justification. The restrictions therefore violate s 2 of the Sherman Act.

2. Integration of IE and Windows

Although Microsoft's license restrictions have a significant effect in closing rival browsers out of one of the two primary channels of distribution, the District Court found that "Microsoft's executives believed ... its contractual restrictions placed on OEMs would not be sufficient in themselves to reverse the direction of Navigator's usage share. Consequently, in late 1995 or early 1996, Microsoft set out to bind [IE] more tightly to Windows 95 as a technical matter." Findings of Fact p 160.

Technologically binding IE to Windows, the District Court found, both prevented OEMs from pre-installing other browsers and deterred consumers from using them. In particular, having the IE software code as an irremovable part of Windows meant that pre-installing a second browser would "increase an OEM's product testing costs," because an OEM must test and train its support staff to answer calls related to every software product preinstalled on the machine; moreover, pre-installing a browser in addition to IE would to many OEMs be "a questionable use of the scarce and valuable space on a PC's hard drive." Id. p 159.

Although the District Court, in its Conclusions of Law, broadly condemned Microsoft's decision to bind "Internet Explorer to Windows with ... technological shackles," Conclusions of Law, at 39, its findings of fact in support of that conclusion center upon three specific actions Microsoft took to weld IE to Windows: excluding IE from the "Add/Remove Programs" utility; designing Windows so as in certain circumstances to override the user's choice of a default browser other than IE; and commingling code related to browsing and other code in the same files, so that any attempt to delete the files containing IE would, at the same time, cripple the operating system. As with the license restrictions, we consider first whether the suspect actions had an anticompetitive effect, and then whether Microsoft has provided a procompetitive justification for them.

a. Anticompetitive effect of integration

As a general rule, courts are properly very skeptical about claims that competition has been harmed by a dominant firm's product design changes. See, e.g., Foremost Pro Color, Inc. v. Eastman Kodak Co., 703 F.2d 534, 544-45 (9th Cir. 1983). In a competitive market, firms routinely innovate in the hope of appealing to consumers, sometimes in the process making their products incompatible with those of rivals; the imposition of liability when a monopolist does the same thing will inevitably deter a certain amount of innovation. This is all the more true in a market, such as this one, in which the product itself is rapidly changing. See Findings of Fact p 59. Judicial deference to product innovation, however, does not mean that a monopolist's product design decisions are per se lawful. See Foremost Pro Color, 703 F.2d at 545; see also Cal. Computer Prods., 613 F.2d at 739, 744; In re IBM Peripheral EDP Devices Antitrust Litig., 481 F. Supp. 965, 1007-08 (N.D. Cal. 1979).

The District Court first condemned as anticompetitive Microsoft's decision to exclude IE from the "Add/Remove Programs" utility in Windows 98. Findings of Fact p 170. Microsoft had included IE in the Add/Remove Programs utility in Windows 95, see id. p p 175-76, but when it modified Windows 95 to produce Windows 98, it took IE out of the Add/Remove Programs utility. This change reduces the usage share of rival browsers not by making Microsoft's own browser more attractive to consumers but, rather, by discouraging OEMs from distributing rival products. See id. p 159. Because Microsoft's conduct, through something other than competition on the merits, has the effect of significantly reducing usage of rivals' products and hence protecting its own operating system monopoly, it is anticompetitive; we defer for the moment the question whether it is nonetheless justified.

Second, the District Court found that Microsoft designed Windows 98 "so that using Navigator on Windows 98 would have unpleasant consequences for users" by, in some circumstances, overriding the user's choice of a browser other than IE as his or her default browser. Id. p p 171-72. Plaintiffs argue that this override harms the competitive process by deterring consumers from using a browser other than IE even though they might prefer to do so, thereby reducing rival browsers' usage share and, hence, the ability of rival browsers to draw developer attention away from the APIs exposed by Windows. Microsoft does not deny, of course, that overriding the user's preference prevents some people from using other browsers. Because the override reduces rivals' usage share and protects Microsoft's monopoly, it too is anticompetitive.

Finally, the District Court condemned Microsoft's decision to bind IE to Windows 98 "by placing code specific to Web browsing in the same files as code that provided operating system functions." Id. p 161; see also id. p p 174, 192. Putting code supplying browsing functionality into a file with code supplying operating system functionality "ensure[s] that the deletion of any file containing browsing-specific routines would also delete vital operating system routines and thus cripple Windows...." Id. p 164. As noted above, preventing an OEM from removing IE deters it from installing a second browser because doing so increases the OEM's product testing and support costs; by contrast, had OEMs been able to remove IE, they might have chosen to pre-install Navigator alone. See id. p 159.

Microsoft denies, as a factual matter, that it commingled browsing and non-browsing code, and it maintains the District Court's findings to the contrary are clearly erroneous. According to Microsoft, its expert "testified without contradiction that '[t]he very same code in Windows 98 that provides Web browsing functionality' also performs essential operating system functions--not code in the same files, but the very same software code." Appellant's Opening Br. at 79 (citing 5 J.A. 3291-92).

Microsoft's expert did not testify to that effect "without contradiction," however. A Government expert, Glenn Weadock, testified that Microsoft "design[ed] [IE] so that some of the code that it uses co-resides in the same library files as other code needed for Windows." Direct Testimony p 30. Another Government expert likewise testified that one library file, SHDOCVW.DLL, "is really a bundle of separate functions. It contains some functions that have to do specifically with Web browsing, and it contains some general user interface functions as well." 12/14/98 am Tr. at 60-61 (trial testimony of Edward Felten), reprinted in 11 J.A. at 6953-54. One of Microsoft's own documents suggests as much. See Plaintiffs' Proposed Findings of Fact p 131.2.vii (citing GX 1686 (under seal) (Microsoft document indicating some functions in SHDOCVW.DLL can be described as "IE only," others can be described as "shell only" and still others can be described as providing both "IE" and "shell" functions)).

In view of the contradictory testimony in the record, some of which supports the District Court's finding that Microsoft commingled browsing and non-browsing code, we cannot conclude that the finding was clearly erroneous. See Anderson v. City of Bessemer City, 470 U.S. 564, 573-74 (1985) ("If the district court's account of the evidence is plausible in light of the record viewed in its entirety, the court of appeals may not reverse it even though convinced that had it been sitting as the trier of fact, it would have weighed the evidence differently."). Accordingly, we reject Microsoft's argument that we should vacate Finding of Fact 159 as it relates to the commingling of code, and we conclude that such commingling has an anticompetitive effect; as noted above, the commingling deters OEMs from pre-installing rival browsers, thereby reducing the rivals' usage share and, hence, developers' interest in rivals' APIs as an alternative to the API set exposed by Microsoft's operating system.

b. Microsoft's justifications for integration

Microsoft proffers no justification for two of the three challenged actions that it took in integrating IE into Windows--excluding IE from the Add/Remove Programs utility and commingling browser and operating system code. Although Microsoft does make some general claims regarding the benefits of integrating the browser and the operating system, see, e.g., Direct Testimony of James Allchin p 94, reprinted in 5 J.A. at 3321 ("Our vision of deeper levels of technical integration is highly efficient and provides substantial benefits to customers and developers."), it neither specifies nor substantiates those claims. Nor does it argue that either excluding IE from the Add/Remove Programs utility or commingling code achieves any integrative benefit. Plaintiffs plainly made out a prima facie case of harm to competition in the operating system market by demonstrating that Microsoft's actions increased its browser usage share and thus protected its operating system monopoly from a middleware threat and, for its part, Microsoft failed to meet its burden of showing that its conduct serves a purpose other than protecting its operating system monopoly. Accordingly, we hold that Microsoft's exclusion of IE from the Add/Remove Programs utility and its commingling of browser and operating system code constitute exclusionary conduct, in violation of s 2.

As for the other challenged act that Microsoft took in integrating IE into Windows--causing Windows to override the user's choice of a default browser in certain circumstances--Microsoft argues that it has "valid technical reasons." Specifically, Microsoft claims that it was necessary to design Windows to override the user's preferences when he or she invokes one of "a few" out "of the nearly 30 means of accessing the Internet." Appellant's Opening Br. at 82. According to Microsoft:

The Windows 98 Help system and Windows Update feature depend on ActiveX controls not supported by Navigator, and the now-discontinued Channel Bar utilized Microsoft's Channel Definition Format, which Navigator also did not support. Lastly, Windows 98 does not invoke Navigator if a user accesses the Internet through "My Computer" or "Windows Explorer" because doing so would defeat one of the purposes of those features-- enabling users to move seamlessly from local storage devices to the Web in the same browsing window.

Id. (internal citations omitted). The plaintiff bears the burden not only of rebutting a proffered justification but also of demonstrating that the anticompetitive effect of the challenged action outweighs it. In the District Court, plaintiffs appear to have done neither, let alone both; in any event, upon appeal, plaintiffs offer no rebuttal whatsoever. Accordingly, Microsoft may not be held liable for this aspect of its product design.