Market Definition and Substitutability- Australian Courts Continue to Struggle with Part IV of the Trade Practices Act 1974 (Cth)

Australian courts have gradually developed a more economics based approach to the interpretation of Part IV of the Trade Practices Act 1974 (Cth). Despite this the courts still appear to encounter difficulties in defining the relevant market in Part IV cases. In particular, courts appear perplexed by market definition and the theory of substitutability. Four recent cases concerned with P&rt IV of the Act, culminating in the deci-sion in News Limited v. Australian Rugby Football League Limited & Ors (the 'Super League case'), are analysed to demonstrate the manner in which courts still strug-gle to apply economic theory to the Act. 1