The Role of Market Definition in Setting Antitrust Fines

The value of sales of an undertaking infringing antitrust law is a key determinant of the size of the fine levied by a competition authority. European competition authorities rely only on the turnover the undertaking receives from the products in relation to which the infringing conduct occurred. In contrast, UK competition authorities may also include revenue from substitutes which the infringing firm supplies. Nonetheless, there are good reasons to include substitutes in the value of sales and, as shown, their inclusion can have a material impact on the size of the fine