In Brown Shoe Co. v. United States (1962) 370 U.S. 294, it is made perfectly clear that no one definition of "substantially," insofar as lessening competition is concerned, was intended by the Congress to control the assessment of mergers, "whether in quantitative terms of sales or assets or market shares or in designated qualitative terms, by which a merger's effects on competition were to be measured." ( Id. at p. 321.) One very important element perceived in Brown was the special situation that prevailed in the particular industry involved. The special situation would take into account factors such as the economic motivation behind the arrangement, its "nature and purpose," and "the trend toward concentration in the industry." To the extent which the Coldwell Banker-Guardian Title arrangement can be regarded as "vertical," Brown aptly points out that "every extended vertical arrangement by its very nature, for at least a time, denies to competitors of the supplier the opportunity to compete for part or all of the trade of the customer-party to the vertical arrangement. However, the Clayton Act does not render unlawful all such vertical arrangements, but forbids only those whose effect 'may be substantially to lessen competition, or to tend to create a monopoly' . . ." ( Brown, supra, 370 U.S. 294.) The Brown court emphasizes the multiplicity of factors present in antitrust determinations -- factors of the kind developed by witnesses, including experts, at the administrative hearings held in the case at bench.