Although some concept of a “market” is inherent in all systems of competition law, the Trade Practices Act 1974 (Cth) is striking in that it expressly makes liability under most of its substantive sections (sections 45, 46, 47, 49 and 50, but not section 48) depend in one way or another on the identification of a market or markets in which competition has been injured by the impugned conduct. This is because at the time when the Trade Practices Act 1974 came to be drafted, the concepts of market definition and market control had evolved to a high level in other jurisdictions, particularly in the United States.
Now, however, after five years’ experience with market definition under the 1974 Act, the Australian doctrine should have its own contribution to make. It should be rewarding, therefore, to attempt to state the principles that have so far emerged, in light also of cases and writings in the major overseas antitrust systems, those of the European Common Market and the United States. Since market definition often determines the outcome of suits or applications under the Trade Practices Act, these principles have practical as well as conceptual importance.