This paper develops a theory of oligopoly and markups in general equilibrium. Firms compete in a network of product … corporations in the USA, using publicly-available data. Using the model, I compute firm-level markups and decompose them into: 1) a … excess of 10 US$ trillions (against $3 trillions of profits). Oligopoly lowers total surplus by 11.5% and depresses consumer …