This paper analyses the regulatory attitudes to asset valuation in the twentieth century. It focuses in particular on the US experience from <italic>Smith v Ames 169 US 466 (1898)</italic> to <italic>Federal Power Commission v Hope Natural Gas 320 US 591 (</italic><italic>1944</italic>) and on the experience in the UK in last two decades of the...

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...