Market definition, and, in particular, being able to identify who is in which product market, lies at the heart of competition law. The identification of demand elasticities necessary to conduct a formal definition of product market can be time consuming and often there is insufficient data to...

The paper outlines various measures of profitability and considers what role they can play in competition law. We argue that profitability measures can provide a good answer to the wrong question and a much less good answer to the question we really want to answer. Using appropriate definitions...