 His conclusion was that monopoly power was not pervasive in the U.S. economy, so that the manufacturing sector could be treated as nearly competitive.Over a decade later, Gordon Tullock argued that Harberger's estimate of the welfare cost of monopoly was low because some resources would be used to compete for or protect monopoly rents, but his argument applies principally to instances of non-price competition for protected status, as in the case of tariffs or restrictions on entry into an industry through government regulation.Harberger's seminal paper on the corporate income tax pioneered the use of general-equilibrium modeling by recasting the classic Heckscher-Ohlin model of international trade as a model of one country with two sectors, one comprising incorporated firms subject to a tax on their net incomes and the other made up of unincorporated firms.