Doubling Back on Double Marginalization

“Double marginalization” and “Elimination of Double marginalization” are catch-phrases commonly used in the IO literature. In this article, I trace back the origin of the idea to Cournot (1838, Ch. IX) on complementary goods monopolies. Through the years Cournot’s contribution remained a reference but ended being viewed as a special case of the bilateral monopoly model. Yet, it is worth wondering why the most cited paper on this issue is nowadays (Spengler in J Polit Econ 58(4):347–352, 1950) which contains only an informal treatment of the question. In addition to retracing the origin of the idea, I emphasize the elegant proof of Cournot for the simultaneous game and extend it to the sequential game. I also show that prices are usually higher in the sequential game but that they could be lower if demand is very convex.