Evolving the Rule of Reason for Legacy Business Conduct

In administering the antitrust laws, is it relevant what a firm’s market power was when a business practice was first implemented? Relatedly, should the commonness of a practice — in terms of use by other firms in a market or industry — be a consideration when assessing its legality? This article proposes that, under certain, well-specified conditions, the legacy of a business practice and its commonness within a market can be used as a “marginally procompetitive presumption” under the