OPINION OF THE COURT
ADAMS, Circuit Judge.
This is the second time this case has come before us. In Larry V. Muko, Inc. v. Southwestern Pennsylvania Building and Construction Trades Council, 609 F.2d 1368 (3d Cir. 1979) [Muko I], this Court, sitting in Banc, reversed a district court order granting defendant’s motion for a directed verdict and remanded the case for a new trial. The second trial resulted in a jury verdict for the defendants, and the plaintiff once again has appealed to this Court. We affirm.
I.
Long John Silver’s, Inc. (“Silver’s”), a Delaware corporation headquartered in Lexington, Kentucky, operates fast food seafood restaurants in several markets across the United States. In 1973, it decided to enter the Pittsburgh, Pennsylvania market, and contracted with Larry V. Muko, Inc. (“Muko”), a non-union general contractor experienced in constructing fast food restaurants, to build its first outlet in Monroe-ville, a suburb of Pittsburgh. After completion of the Monroeville restaurant, Silver’s president Jim Patterson met with Larry Muko and indicated his willingness to give future construction business to Muko if his prices remained competitive and the quality of his construction remained good. Muko was awarded a contract to build a second restaurant in Lower Burrell, Pennsylvania, but Silver’s did not commit itself any further.
During construction of the Monroeville restaurant, two labor organizations, the Southwestern Pennsylvania Building and Construction Trades Council and the Building and Construction Trades Council of Pittsburgh (the “Councils”), picketed the site. After completion of construction, handbills were distributed to customers of the Monroeville restaurant urging them not to patronize Silver’s because the chain used “contractors who are paying less than the established prevailing wages in the area.” Appendix at 115a. The handbill exhorted the customers “to protect the living and working standards established by the Building Trades Council.” Id.
Silver’s management was alarmed when it was informed that customers were leaving the premises after reading the handbill. In response to the leafletting, Silver’s arranged a meeting with the Building Trades Councils. After the meeting, Silver’s vice-president sent a letter to the Councils emphasizing the company’s “desire to establish good working relationships with the unions in the Greater Pittsburgh Area” and stating Silver’s “intent ... to use only union contractors certified by the [Councils]” in the future. The letter concluded: “In any relationship between two parties there must be mutual need and assistance. ... It is . . . extremely important to both parties that our location at Monroeville, Pennsylvania and the one under construction in Low-, er Burrell Township, Pennsylvania not be subjected to any kind of informational pick- . eting.” Appendix at 116a-117a.
Subsequently, Silver’s employed only unionized general contractors to build its Pittsburgh-area restaurants, although the general contractors were free to use nonunion subcontractors. Silver’s discussed with Muko the question whether Muko would be willing to bid on the construction . of its restaurants as a union firm. Muko declined to build under such circumstances, [424]*424however, and it was not awarded any of Silver’s contracts after the construction of the Lower Burrell restaurant.
On August 12, 1975, Muko filed the present lawsuit against Silver’s and the two Councils, alleging that the defendants had entered into an agreement to award contracts for the construction of Silver’s restaurants in the Pittsburgh area only to union contractors. This, claimed Muko, was an unreasonable restraint of trade in violation of section 1 of the Sherman Act and sections 4 and 16 of the Clayton Act. After Muko presented its case at a jury trial held on July 19-20, 1977, the district court granted the defendants’ motion for a directed verdict. The directed verdict apparently was granted “because the court believed the evidence could sustain no finding other than a unilateral decision on the part of Silver’s to accept bids only from union contractors.” 609 F.2d at 1372. On appeal, this Court, sitting in banc, reversed and remanded the case for a new trial. 609 F.2d 1368. We held that the jury could have found an agreement between Silver’s and the Councils that was not exempt from antitrust scrutiny because, under the standards set forth in Connell Construction Co. v. Plumbers & Steamfitters Local 100, 421 U.S. 616, 95 S.Ct. 1830, 44 L.Ed.2d 418 (1975), such an agreement might have “actual or potential anticompetitive effects that would not flow naturally from the elimination of competition over wages and working conditions.” 609 F.2d at 1373.
Upon remand, a bifurcated jury trial on issues of liability and damages took place. At the close of the evidence on liability, the district court submitted four special interrogatories to the jury:
1. Did Long John Silver’s and the Trade Councils enter into an agreement or combination to refuse to grant construction contracts to non-union builders, including Muko?
Answer: YES_ NO_
If your answer to question 1. is NO, go no further. If your answer to question 1. is YES, go on to question 2.
2. Was the effect of the agreement between Long John Silver’s and the Trade Councils to impose a restraint on free competition beyond that which would follow from the elimination of competition based on wage rates and working conditions?
Answer: YES_ NO-
If your answer to question 2. is NO, go no further. If your answer to question 2. is YES, go on to question 3.
3. Was the agreement between Long John Silver’s and the Trade Councils an unreasonable restraint of trade under the standards given you by the court in its instructions?
Answer: YES_ NO_
If your answer to question 3. is NO, go no further. If your answer to question 3. is YES, go on to question 4.
4. Did the agreement between Long John Silver’s and the Trade Councils cause injury to the plaintiff in his business or property?
Answer: YES. NO_
On February 17, 1981, the jury returned its verdict, answering “Yes” to Interrogatories 1 and 2 and “No” to Interrogatory 3. The jury thus found that the defendants had reached an agreement, outside the labor exemption, to exclude Muko as a competitor for Silver’s construction work. Because the jury concluded that the agreement was not an unreasonable restraint of trade, however, the district court entered judgment for the defendants. The district court subsequently denied Muko’s motion for a new trial and denied defendants’ conditional motions for judgment n. o. v. This appeal followed.
II.
Muko challenges two aspects of the district court proceeding. First, it claims that the trial judge erred as a matter of law when he instructed the jury to apply the rule of reason, rather than the per se standard, to the agreement at issue. Second, it argues that, even if the district judge was correct in applying the rule of reason, he erred in his instructions on the relevant [425]*425product market. We disagree with both contentions.1
III.
A.
In the earlier in banc opinion in this case, we declined to decide the proper standard by which to measure any potential antitrust violation. We intimated, however, that traditional antitrust principles would govern such a determination by the district court:
The jury might have found a concerted refusal to deal with a class of contractors of which Muko is a member. But whether the evidence here is viewed as capable of sustaining a finding of a group boycott, to which a per se rule would apply, or some lesser restraint to which a rule of reason analysis might apply, it was sufficient to take Muko’s case to the jury. We have no occasion on this record to rule on whether, after hearing the defendants’ evidence as well, the court should instruct the jury that it should measure the agreement by rule of reason or per se standards.
609 F.2d at 1376 (footnote omitted).
In counseling that the level of antitrust inquiry depends upon the nature of the conduct alleged, even in the labor-antitrust context, Muko I reflected the approach taken by a panel of this Court in Consolidated Express, Inc. v. New York Shipping Association, 602 F.2d 494 (3d Cir. 1979), vacated and remanded on other grounds, 448 U.S. 902, 100 S.Ct. 3040, 65 L.Ed.2d 1131 (1980) [“Conex”], a case decided several months prior to Muko I. There, the plaintiff was a freight consolidator whose business was threatened after defendants New York Shipping Association (an association of employers) and the longshoremen’s union negotiated “Rules on Containers” and the so-called “Dublin Supplement” in response to the perceived threat to waterfront labor posed by technological change in the shipping industry. Conex claimed, inter alia, that the defendants’ enforcement of the rules constituted a group boycott of the plaintiffs that was illegal per se under the Sherman Act.2 We held, as an initial matter, “that the proper method of analysis is to determine the issue of nonstatutory labor exemption separately, . . . and then to proceed with conventional antitrust scrutiny of the complaint.” 602 F.2d at 522. In so holding, the Conex Court expressly rejected Professor Handler’s view “that there be a full-scale rule of reason inquiry in every instance in which a non-exempt activity is claimed to be in violation of antitrust.” Handler, Labor and Antitrust: A Bit of [426]*426History, 40 Antitrust L.J. 233, 239-40 (1971). Pointing to United Mineworkers v. Pennington, 381 U.S. 657, 85 S.Ct. 1585, 14 L.Ed.2d 626 (1965), and its companion case, Local 189, Amalgamated Meat Cutters v. Jewel Tea Co., 381 U.S. 676, 85 S.Ct. 1596, 14 L.Ed.2d 640 (1965), Judge Gibbons concluded: “[T]he three groups of Justices in those cases, while they diverged widely on other issues, appear to have agreed that ‘settled antitrust principles’ would be ‘appropriate and applicable’ to activity found to be nonexempt. . . . Those ‘settled’ principles include the per se rule, where the facts warrant its application.” 602 F.2d at 522-23 (emphasis added).
We take this opportunity explicitly to reaffirm the holding in Conex, as reflected implicitly in Muko I. In so doing we adopt a middle position between that advocated by Professor Handler and that proposed by the appellant in the case at hand. While we agree with Professor Handler that the “factors to be considered in determining the existence of an antitrust exemption are separate and distinct from those bearing on the presence of an antitrust infraction,” and that “once such conduct is deemed not exempt, it is incumbent upon the decisionmaker to consider the relative anticompetitiveness of the conduct before imposing antitrust liability,” Handler & Zifchak, Collective Bargaining and the Antitrust Laws: The Emasculation of the Labor Exemption, 81 Colum.L.Rev. 459, 51-1 (1981), we do not share Professor Handler’s view that union conduct necessarily “should be measured by the rule of reason in recognition of the peculiar labor relations context in which the restraint arises even if, in a nonlabor context, similar conduct might be per se unlawful.” Id. at 510.3 The mere fact that a labor union is one of the participants in an otherwise illegal combination should not preclude a determination that, in appropriate circumstances, the conduct is unreasonable per se. See, e.g., Allen Bradley Co. v. Local 3, International Brotherhood of Electrical Workers, 325 U.S. 797, 65 S.Ct. 1533, 89 L.Ed. 1939 (1945). The per se rule is, essentially, a short cut employed by a court in determining unreasonableness; as Professor Sullivan has taught, “the per se doctrine is precisely a special case of rule of reason analysis.” L. Sullivan, Handbook of the Law of Antitrust (1977). See discussion in part III(B) infra. If, after extensive experience with a particular kind of union conduct, a court concludes that the conduct invariably restrains competition, it is unnecessary, in our view, for the court to engage in lengthy rule-of-reason analysis when the per se rule would yield identical results more efficiently and expeditiously.
It is important, however, to caution against mechanical or imprudent application of the per se rule in the labor context. A finding that particular union conduct has anticompetitive effects that do “not flow naturally from the elimination of competition over wages and working conditions,” and hence is non-exempt under Connell, should not drive a court inexorably to the conclusion that the union has violated the antitrust laws. We thus cannot agree with Muko, who contends that every labor-antitrust case in which the labor exemption is found to be inapplicable should be held illegal under the per se standard.
In support of this proposition Muko points to the following language in the Co-nex opinion:
[0]nce a court has concluded that the labor exemption does not shield anticompetitive conduct, application of the rule of reason is redundant. The justification offered for application of the rule of reason is the need to recognize, in the antitrust context, labor’s legitimate interest in the collective bargaining process. [427]*427That interest, however, is precisely the same one that must be taken into account in determining the scope of the nonstatutory labor exemption. A holding that the exemption does not apply embodies a judgment that considerations of labor policy are outweighed by the anticompetitive dangers posed by the challenged restraint. The proposed use of the rule of reason would, therefore, simply be an invitation to the court or jury to reweigh under a different label the question of the non-statutory exemption.
602 F.2d at 523-24.
Although this language appears to support Muko’s contention, the actual holding in Conex is far narrower in scope. In Co-nex, in fact, this Court carefully analyzed the conduct in question before determining that it constituted a per se illegal group boycott. See discussion in part III(B) infra. Indeed, the Court suggested that had pro-competitive effects been shown, the boycott may have been removed from the category of per se violations. See 602 F.2d at 524 n.18 and accompanying text. As the Conex majority points out, “public interest” considerations, such as the advancement of labor policy, are not proper subjects for examination under the rule of reason. National Society of Professional Engineers v.
United States, 435 U.S. 679, 688, 98 S.Ct. 1355, 1363, 55 L.Ed.2d 637 (1978).4 The passage from Conex quoted above merely reflects the view that it is unnecessary, if not improper, to weigh “labor’s legitimate interest in the collective bargaining process” twice — once in determining the labor exemption and again in deciding the antitrust liability question. See Casey & Cozzil-Iio, supra note 3, at 271. There is no indication that the Court was prepared to find that the defendants’ conduct was per se illegal merely because it was not exempt from the antitrust laws.5 Moreover, in Muko I, Judge Gibbons — who earlier had written Conex — explicitly left open the possibility that a “lesser restraint,” though nonexempt, might be judged under the rule of reason. 609 F.2d at 1376. But see King & Moser, Muko and Conex: The Third Circuit Responds to Connell, 8 Pepperdine L.Rev. 79 (1980).
In short, a fair reading of both Conex and Muko I impels the conclusion that, once it is ascertained that union activity falls outside the protection of the labor exemption, a court must apply traditional antitrust principles in determining whether the activity in question violates the antitrust laws.6 In most cases the rule of rea[428]*428son will supply the measure of illegality; the per se rule may, however, be invoked where appropriate. We turn now to this inquiry.
B.
Though framed in absolute terms, section 1 of the Sherman Act7 has been construed throughout its history to proscribe only unreasonable restraints of trade. Chicago Board of Trade v. United States, 246 U.S. 231, 38 S.Ct. 242, 62 L.Ed. 683 (1918); Standard Oil Co. v. United States, 221 U.S. 1, 31 S.Ct. 502, 55 L.Ed. 619 (1911). In most cases, a “rule of reason” analysis requires a detailed examination of the affected business and the nature of the restraint imposed.8 There are, however, “certain agreements or practices which because of their pernicious effect on competition and lack of any redeeming virtue are conclusively presumed to be unreasonable and therefore illegal without elaborate inquiry as to the precise harm they have caused or the business excuse for their use.” Northern Pacific Railway Co. v. United States, 356 U.S. 1, 5, 78 S.Ct. 514, 518, 2 L.Ed.2d 545 (1958). Such determinations of per se illegality are not casually made. As the Supreme Court noted in United States v. Topco Associates, 405 U.S. 596, 607-08, 92 S.Ct. 1126, 1133, 31 L.Ed.2d 515 (1972), and as our Court reiterated most recently in Tose v. First Pennsylvania Bank, 648 F.2d 879, 891 (3d Cir.), cert. denied, - U.S. -, 102 S.Ct. 390, 70 L.Ed.2d 208 (1981), “[ijt is only after considerable experience with certain business relationships that courts classify them as per se violations of the Sherman Act.” See Cernuto, Inc. v. United Cabinet Corp., 595 F.2d 164, 166-67 (3d Cir. 1979); Harold Friedman Inc. v. Thorofare Markets Inc., 587 F.2d 127, 140 (3d Cir. 1978).9 Neither mere speculation, nor the desire to simplify the cumbersome process of determining antitrust illegality, is enough to justify the imposition of a per se rule. In Tose, for example, we declined to extend the per se rule to an agreement to force a distress sale of a partner’s share of a business because we were “not aware of any body of judicial experience teaching” that such an agreement had a “ ‘pernicious effect on competi[429]*429tion ....’” 648 F.2d at 891. In short, “departure from the rule-of-reason standard must be based upon demonstrable economic effect rather than . . . upon formalistic line drawing.” Continental T.V., Inc. v. GTE Sylvania Inc., 433 U.S. 36, 58-59, 97 S.Ct. 2549, 2561-2562, 53 L.Ed.2d 568 (1977) (emphasis added).
Group boycotts have typically been among those categories of conduct deemed unreasonable per se. See, e.g., United States v. General Motors Corp., 384 U.S. 127, 86 S.Ct. 1321, 16 L.Ed.2d 415 (1966); Klor’s, Inc. v. Broadway-Hale Stores, Inc., 359 U.S. 207, 79 S.Ct. 705, 3 L.Ed.2d 741 (1959); Fashion Originators’ Guild of America, Inc. v. FTC, 312 U.S. 457, 61 S.Ct. 703, 85 L.Ed. 949 (1941). In Klor’s, supra, for example, the Supreme Court condemned as unlawful an agreement between a large chain department store and a group of manufacturers and distributors not to deal with a smaller, competing retail store. The Court declared:
Group boycotts, or concerted refusals by traders to deal with other traders, have long been held to be in the forbidden category. They have not been saved by allegations that they were reasonable in the specific circumstances, nor by a failure to show that they “fixed or regulated prices, parcelled out or limited production, or brought about a deterioration in quality.” Fashion Originators’ Guild v. Federal Trade Comm’n, 312 U.S. 457, 466, 467-468 [61 S.Ct. 703, 707, 708, 85 L.Ed. 949]. Cf. United States v. Trenton Potteries Co., 273 U.S. 392 [47 S.Ct. 377, 71 L.Ed. 700]. Even when they operated to lower prices or temporarily to stimulate competition they were banned. For, as this Court said in Kiefer-Stewart Co. v. Seagram & Sons, 340 U.S. 211, 213 [71 S.Ct. 259, 260, 95 L.Ed. 219], “such agreements, no less than those to fix minimum prices, cripple the freedom of traders and thereby restrain their ability to sell in accordance with their own judgment.” Cf. United States v. Patten, 226 U.S. 525, 542, 33 S.Ct. 141, 145, 57 L.Ed. 333.
359 U.S. at 212, 79 S.Ct. at 709 (footnote omitted) (emphasis added).
Though Klor’s appears flatly to proscribe group boycotts, whatever their form or function, courts and commentators 10 alike continue to resist the notion that all concerted refusals to deal fall automatically as per se violations of the antitrust laws. Generally, the application of the per se rule has been limited to those “classic” boycotts in which a group of business competitors seek to benefit economically by excluding other competitors from the marketplace.11 “The crucial element” in such boycotts, according to Professor Sullivan, “is an effort [430]*430to exclude or cause disadvantage to one or more competitors by cutting them off from trade relationships which are necessary to any firm trying to compete. The classic boycott . . . also usually entails an effort to induce two or more suppliers or customers not to deal with firms being excluded from the protected level.” L. Sullivan, Handbook of the Law of Antitrust 260 (1977).
While the Supreme Court has not confronted this issue directly, a survey of the Court’s group boycott decisions in which the per se rule was invoked “confirms that it is attempts by competitors to exclude horizontal competitors which trigger the per se rule.” Comment, Protest Boycotts Under the Sherman Act, 128 U.Pa.L.Rev. 1131, 1151 (1980). In Klor’s, for example, the unlawful conduct was the attempt by one retailer to push a competitor out of the market. Similarly, in Radiant Burners, Inc. v. Peoples Gas Light & Coke Co., 364 U.S. 656, 81 S.Ct. 365, 5 L.Ed.2d 358 (1961), the plaintiff, a gas burner manufacturer, complained that the arbitrary denial of a gas association’s “seal of approval” prevented the company from competing with the manufacturer-members of the association. The Supreme Court held that the plaintiff was entitled to a trial on these allegations. In United States v. General Motors Corp., 384 U.S. 127, 79 S.Ct. 705, 3 L.Ed.2d 741 (1966), a scheme in which retailers induced a manufacturer not to sell to competing discount retailers was held illegal per se under the Sherman Act. And in Fashion Originators’ Guild of America, Inc. v. FTC, 312 U.S. 457, 61 S.Ct. 703, 85 L.Ed. 949 (1941), the Court concluded that the per se rule was appropriate where one group of manufacturers attempted to induce retailers not to buy from another group of manufacturers. Significantly, while the Supreme Court recently declined to limit, for purposes of the McCar-ran-Ferguson Act, the definition of the term “boycott” to “those combinations which target competitors of the boycotters as the ultimate objects of a concerted refusal to deal,” the Court did intimate that it was willing to distinguish between those boycotts that were unreasonable per se and those that were not. St. Paul Fire & Marine Insurance Co. v. Barry, 438 U.S. 531, 542, 98 S.Ct. 2923, 2930, 57 L.Ed.2d 932 (1978). Noting the continuing controversy over the definition of the per se illegal boycott, the Court declared: “But the issue before us is whether the conduct in question involves a boycott, not whether it is per se unreasonable.” Id. See Bauer, Per Se Illegality of Concerted Refusals to Deal: A Rule Ripe for Reexamination, 79 Colum.L. Rev. 685, 691-92 (1979).
Our circuit is among those that have attempted to limit the application of the per se rule to the “classic” boycott. As we stated in DeFilippo v. Ford Motor Co., 516 F.2d 1313, 1317 (3d Cir.) cert. denied, 423 U.S. 912, 96 S.Ct. 216, 46 L.Ed.2d 141 (1975):
The inquiry in any case seeking to apply this rule of per se unreasonableness must be whether or not the activities of defendants properly fall within the “group boycott” categorization. . .. “The term ‘group boycott’ ... is in reality a very broad label for divergent types of concerted activity. To outlaw certain types of business conduct merely by attaching the ‘group boycott’ and ‘per se’ labels obviously invites the chance that certain types of reasonable concerted activity will be proscribed.”
Id. at 1317-18 (quoting Worthen Bank & Trust Co. v. National Bank Americard, Inc., 485 F.2d 119, 125 (8th Cir. 1973), cert. denied, 415 U.S. 918, 94 S.Ct. 1417, 39 L.Ed.2d 473 (1974)).
In DeFilippo, we concluded, after surveying the relevant Supreme Court precedents, that a concerted activity constitutes a per se illegal “group boycott” only when “ ‘there [is] a purpose either to exclude a person or group from the market, or to accomplish some other anti-competitive objective, or both.’ ” 516 F.2d at 1318 (quoting Joseph E. Seagram & Sons, Inc. v. Hawaiian Oke & Liquors, Ltd., 416 F.2d 71, 76 (9th Cir. 1969), cert. denied, 396 U.S. 1062, 90 S.Ct. 752, 24 L.Ed.2d 755 (1970)). There, the defendant, Ford Motor Company, had refused to consummate a “special terms” arrangement between it and oné of its deal[431]*431ers, after other area dealers protested, cause this refusal did not deprive plaintiffs of the opportunity to become a Ford dealer, or to purchase products on the same basis as other dealers, we held that the concerted action at issue in the case “did not constitute a group boycott in the sense of a per se unreasonable restraint of trade.” Id. at 1320 (emphasis added). Be-
More recently, in Sitkin Smelting & Refining Co. v. FMC Corp., 575 F.2d 440 (3d Cir.), cert. denied, 439 U.S. 866, 99 S.Ct. 191, 58 L.Ed.2d 176 (1978), we again faced the problem of defining the term “group boycott” and determining the bounds of its legality. In Sitkin, the plaintiff complained that the defendant had engaged in a sham bidding scheme with a third party whereby the defendant agreed that the third party would be awarded a contract to dismantle defendant’s rayon plant if it matched the bid of the otherwise highest bidder. The Court declined to hold that this conduct constituted an illegal group boycott: “The controlling cases involve broad combinations and rather pervasive refusals to deal by a group of suppliers covering many transactions over an extended period of time.... We are not confronted with such a factual situation here. Plaintiffs have not brought to our attention any case where a court has found a per se violation of the Sherman Act on the basis of a concerted refusal to deal between a single seller and a single buyer.” 575 F.2d at 446-47 (citations omitted).
In contrast, the Court indicated its willingness to apply the per se rule in Cernuto, Inc. v. United Cabinet Corp., 595 F.2d 164 (3d Cir. 1979). There, the manufacturer of kitchen cabinets allegedly terminated its sales to a discount retailer at the urging of another competing retailer, who wished to maintain prices. Like Klor’s and General Motors, the case involved the attempt of one competitor to squeeze out its direct competitor. “[Although the termination in such a situation is, itself, a vertical restraint, the desired impact is horizontal and on the dealer, not the manufacturer, level.” 595 F.2d at 168. Thus, we reversed the summary judgment entered in favor of the defendants on the ground that at trial a per se violation of the Sherman Act might be found. See Comment, Vertical Agreement as Horizontal Restraint: Cernuto, Inc. v. United Cabinet Corp., 128 U.Pa.L.Rev. 622 (1980).
Finally, in Conex, discussed supra, we addressed the question whether a group boycott in the labor context was per se unreasonable. There, we outlined a “core group of situations” in which group boycotts have been deemed illegal per se:
(1) horizontal combinations of traders at one level of distribution having the purpose of excluding direct competitors from the market, e.g., Associated Press v. United States, 326 U.S. 1, 65 S.Ct. 1416, 89 L.Ed. 2013 (1945); Eastern States Retail Lumber Dealers’ Ass’n v. United States, 234 U.S. 600, 34 S.Ct. 951, 58 L.Ed. 1490 (1914); (2) vertical combinations, designed to exclude from the market direct competitors of some members of the combination, e.g., Klor’s, Inc. v. Broadway-Hale Stores, Inc., 359 U.S. 207, 79 S.Ct. 705, 3 L.Ed.2d 741 (1959); and (3) coercive combinations aimed at influencing the trade practices of boycott victims. E.g., Kiefer-Stewart Co. v. Joseph E. Seagram & Sons, Inc., 340 U.S. 211, 71 S.Ct. 259, 95 L.Ed. 219 (1951); Fashion Originators’ Guild of America v. Federal Trade Commission, 312 U.S. 457, 61 S.Ct. 703, 85 L.Ed. 949 (1941).
602 F.2d at 522. See E. A. McQuade Tours, Inc. v. Consolidated Air Tour Manual Committee, 467 F.2d 178, 186-87 (5th Cir. 1972), cert. denied, 409 U.S. 1109, 93 S.Ct. 912, 34 L.Ed.2d 690 (1973).
In Conex, after holding that the Rules on Containers and the Dublin Supplement were not exempt from the antitrust laws, the Court concluded that the facts of the case did warrant the application of the per se rule. Specifically, we found that the rules had “horizontal, vertical, and coercive aspects”: the goal of the union organization was “work acquisition” because the “union’s efforts clearly were directed toward the elimination of teamster competition”; the [432]*432rules “wholly bar” the plaintiffs from providing their services in the market in question; the “anticompetitive effect of [the] arrangement [was] clear”; nor was there “any suggestion in the record that the application of the Rules will in the long run have procompetitive rather than anticom-petitive effects.” In sum, the Court determined that the rules represented “ ‘agreements whose nature and necessary effect are so plainly anticompetitive that no elaborate study of the industry is needed to establish their illegality.’ ” Conex at 522-23, (quoting National Society of Professional Engineers v. United States, 435 U.S. 679, 98 S.Ct. 1355, 55 L.Ed.2d 637 (1978)).
C.
Applying the foregoing principles to the case at hand, we conclude that the agreement between Silver’s and the Trade Councils should not be deemed unreasonable per se. A distillation of the facts at issue here makes it clear that this is not a classic group boycott; the defendants’ conduct should not be proscribed until the fact-finder has been given the opportunity to determine its reasonableness. Simply put, a small retailer has been picketed by a union. To preserve its business, the firm agrees to purchase union-made goods or services in the future. We cannot agree with Muko or the dissent that this is the kind of behavior against which the per se rule traditionally has been invoked. Unlike Klor’s and General Motors, this is not a case in which one competitor, through concerted action with a supplier or customer, attempts to cut another, horizontal competitor out of the marketplace. Nor is there any suggestion of attempted price-fixing, as in Cernuto. Notwithstanding the dissent’s assertion, which is not groundéd on record evidence, that Muko “must be viewed as the representative of non-union labor,” the fact remains that neither Silver’s nor the Trades Councils was in competition with each other or with Muko. There is no evidence that Silver’s goal was to affect Muko’s business; rather, it is uncontradicted that Silver’s sought only to retain the goodwill of its customers in a new market. The Councils’ goal was to ensure payment of the prevailing union wage to Pittsburgh-area construction workers. The record is barren of anything to suggest that either of the defendants wished, through their concerted action, to gain an advantage over Muko in an economic or competitive sense. This fundamentally distinguishes the present case from Conex, which involved an agreement between the defendant longshoremen’s union, common carriers, and stevedores to exclude from direct competition all the teamsters employed by the plaintiff freight consolidators.
We note, too, the limited nature of the restraint at issue here. Unlike Conex, in which the defendant union imposed a widespread restraint of trade, affecting the entire shipping industry, the “refusal to deal” in this case involved only one relatively small buyer: Silver’s. Moreover, we fail to perceive the significant anticompetitive effects alleged by the appellant. Again, unlike Conex, the agreement did not have the necessary effect of destroying Muko’s business; indeed, the evidence shows that Muko’s profits increased during the time in question. Appendix at 127a. Silver’s also appeared prepared to give Muko the job of constructing future restaurants if Muko employed union labor. Finally, procompeti-tive effects were demonstrated — Silver’s gained a position in the otherwise crowded Pittsburgh-area fast food market.
The dissent points to a series of cases in an effort to support its view that Silver’s agreement not to employ non-union contractors is unreasonable per se. None is apposite. Most of the cases cited—Klor’s Fashion Originators’, Radiant Burners, and Cernuto, discussed supra—involve horizontal restraints (or, perhaps more accurately, vertical restraints with horizontal effects) by direct competitors. Similarly, United States v. Topco Associates, 405 U.S. 596, 92 S.Ct. 1126, 31 L.Ed.2d 515 (1972), involved a horizontal territorial restraint. Another case, National Society of Professional Engineers v. United States, 435 U.S. 679, 98 S.Ct. 1355, 55 L.Ed.2d 637 (1978), a suit brought by the Government to nullify a [433]*433professional association’s canon of ethics prohibiting competitive bidding, was decided under the rule of reason. Indeed, Continental T.V., Inc. v. GTE Sylvania Inc., 433 U.S. 36, 97 S.Ct. 2549, 53 L.Ed.2d 568 (1977), overruled the per se rule of United States v. Arnold, Schwinn & Co., 388 U.S. 365, 87 S.Ct. 1856, 18 L.Ed.2d 1249 (1967) that had previously governed vertical restraints. United States v. Philadelphia National Bank, 374 U.S. 321, 83 S.Ct. 1715, 10 L.Ed.2d 915 (1963), cited by the dissent for the proposition that a procompetitive effect in one market will not excuse an anticom-petitive effect in another, was a merger case under section 7 of the Clayton Act, 15 U.S.C. § 18. The defendants sought to defend their merger in part on the proposition that “if all the commercial banks in the Philadelphia area merged into one, it would be smaller than the largest bank in New York City.” 374 U.S. at 370, 83 S.Ct. at 1745. While the Court rejected this argument as a justification for a merger, it in no way addressed the question whether pro-competitive effects could be considered in making the initial determination whether conduct was so pernicious as to be illegal per se under section 1 of the Sherman Act. And, finally, in St. Paul Fire & Marine Insurance Co. v. Barry, 438 U.S. 531, 542, 98 S.Ct. 2923, 2930, 57 L.Ed.2d 932 (1978), discussed supra, the Supreme Court explicitly declined to address the question whether all boycotts were unreasonable per se.
In sum, we have been referred to no case that suggests that the agreement at issue here is one “whose nature and necessary effect [is] so plainly anticompetitive that no elaborate study of the industry is needed.... ” Conex at 522-23. Accordingly, we hold that the district court did not err in instructing the jury to apply the rule of reason, rather than the per se standard, to the conduct in question in this case.
IV.
We turn now to Muko’s second contention in this appeal — that the district court erred in instructing the jury on the relevant product market.
At trial, Muko’s expert testified that the relevant product market was the construction of fast food restaurants. Defendants contended that the relevant product market was the construction of small commercial buildings, including fast food restaurants. The trial judge instructed the jury that it could consider whether the construction of fast food restaurants was
a type of trade in which the contractors limit themselves or specialize in to the exclusion of other lines; is the construction of fast food restaurants, from what you have heard in the evidence here, a line of trade, a real line of trade in which somebody either devotes all his time, he doesn’t do anything else, or a majority of his time or is that bigger? Do contractors in general — not necessarily the plaintiff here, all of them, do they regard this as an activity in which they devoted their time and energy and assets to so that, if that is blocked, they can’t easily change to another line? . . .
If this agreement puts a restraint only on fast food restaurants, is that sufficiently reasonable for your consideration, or can contractors who do fast food restaurants just as easily do convenience stores, 7-Eleven Stores, small business buildings, branch banks? Is the line of trade confined to restaurants, or is it a little bigger, to include, as has been argued here, small commercial buildings?
Appendix at 1253a-1254a.
Muko objects to the trial court’s instruction in this respect because the charge “made definition of the market and reasonableness of the restraint dependent upon Muko’s ability to compete in a market other than the one in which the alleged restraint occurred.” Brief for Appellant at 21. It points to cases such as Brown Shoe Co. v. United States, 370 U.S. 294, 82 S.Ct. 1502, 8 L.Ed.2d 510 (1962) and United States v. E.I. DuPont de Nemours & Co., 351 U.S. 377, 76 S.Ct. 994, 100 L.Ed. 1264 (1956), arguing that the fact that “the defendant in DuPont was presumably able to make wrapping products other than cellophane” was not relevant to a determination of the product [434]*434market: “The law does not, however, define either the product market or the reasonableness of a restraint in terms of the versatility of the alleged antitrust victim.” Brief for Appellant at 33.
In a traditional section 2 monopolization case, the “product market” is defined in terms of cross-elasticity of demand — can the consumer of the product of an alleged monopolist switch easily to a substitute product, thereby undercutting the monopolist’s power? See Brown Shoe, supra. As this Court held in SmithKline Corp. v. Eli Lilly and Co., 575 F.2d 1056 (3d Cir.), cert. denied, 439 U.S. 838, 99 S.Ct. 123, 58 L.Ed.2d 134 (1978):
defining a relevant product market is a process of describing those groups of producers which, because of the similarity of their products, have the ability — actual or potential — to take significant amounts of business away from each other. A market definition must look at all relevant sources of supply, either actual rivals or eager potential entrants to the market.
575 F.2d at 1063. See also Coleman Motor Co. v. Chrysler Corp., 525 F.2d 1338, 1349 (3d Cir. 1975) (emphasizing “interchangeability” of products).
It should be remembered that this case is not a monopolization case; nor is it a restraint of trade by producers of the product. Here, the consumers of Muko’s product (construction services) have contracted to restrain trade. Thus the market must be analyzed not in terms of cross-elasticity of demand for the product, but of cross-elasticity of supply. That is, can Muko easily substitute one product (any type of small commercial building) for another (fast food restaurants)?
Under this analysis, Muko’s argument fails to withstand scrutiny. The district court did not instruct the jury to decide whether, if pushed out of the “relevant product market,” Muko could enter a new, unrelated market. It simply asked the jury to determine whether Muko’s “line of trade” was confined to fast food restaurants or whether it included other sorts of small commercial buildings. We find no error in this instruction.
V.
To summarize, we hold that the district court correctly instructed the jury on the rule of reason standard as well as on the relevant product market. Accordingly, the order of the district court, entering judgment for the defendants, will be affirmed.12