y would this require antitrust courts to make the type of regulatory assessments that Trinko recognized they are ill suited to perform but, in addition, simply managing output falls outside antitrust's purpose, which is to make markets more competitive by breaking down monopolies rather than merely requiring that they be shared (Areeda and Hovenkamp 2008c; Speta 2006). Judicial imposition of retail access has been based not on the antitrust laws, but rather on the common law duty to serve imposed on businesses "affected with the public interest." This concept received its fullest exposition when the Court established in Munn V. Illinois that businesses affected with a public interest represented an exception to the constitutional limits on regulation imposed by the Lochner era conception of economic rights protected by substantive due process (94 U.S. 113, 126 (1876)). The Court abandoned this line of jurisprudence in its landmark opinion in Nebbia V. New York, in which the Court concluded that "there is no closed class or category of businesses affected with a public interest." The Court further elaborated: In several of the decisions of this court wherein the expressions "affected with a public interest," and "clothed with a public use," have been brought forward as the criteria of the validity of price control, it has been admitted that they are not susceptible of definition and form an unsatisfactory test of the constitutionality of legislation directed at business practices or prices. (291 U.S. 502, 536 (1934))¹ 99 This is true regardless of whether the natural monopoly arises because of declining average costs or network economic effects (Lemley and McGowan 1998). 100 See also Am. Football League V. Nat'l Football League, 323 F.2d 124, 131 (4th Cir. 1963); Lamb Enters., Inc. V. Toledo Blade Co., 461 F.2d 506, 515 (6th Cir. 1972); Greenville Publ'g Co. V. Daily Reflector, Inc., 496 F.2d 391, 397 (4th Cir. 1974); Hecht, 570 F.2d at 990-91; Alaska Airlines, 948 F.2d at 548. 101 See also Jackson V. Metro. Ediso