The invention of the price/cost margin (P-MC)/P as an index of market power is usually credited to Lerner (Rev Econ Stud 1(3):157–175, <CitationRef CitationID="CR28">1934</CitationRef>). Landes and Posner (Harv Law Rev 94(5):937–996, <CitationRef CitationID="CR26">1981</CitationRef>) is similarly often considered the main reference for the generalized version of the index in the...</citationref></citationref>