Third, the government's concessions. The government often implements monopoly policies in certain industries, such as railway transportation departments, power supply and water supply departments, etc. So exclusive enterprises become monopolists in these industries.
Fourth, natural monopoly. The production of some industries has such characteristics: the economies of scale of enterprise production need to be fully reflected in a large output range and the corresponding production and operation level of huge capital equipment, so that the output of the whole industry can only be achieved by one enterprise. And as long as we give full play to the production capacity of this enterprise on this production scale, we can meet the demand of the whole market for this product. In the production of such products, there will always be a manufacturer in the industry who will take the lead in reaching this production scale with strong economic strength and other advantages, thus monopolizing the production and sales of the whole industry. This is natural monopoly. The production of some industries needs to invest a lot of fixed assets and funds. If we give full play to these fixed assets and funds, this industry can meet the product supply of the whole market with only one enterprise. Such enterprises are suitable for mass production. Production on this scale is economical, and production below this scale is not economical. In this way, economies of scale become an important reason for the formation of monopoly. At the same time, the full play of a large number of fixed assets and funds has enabled enterprises to have the ability and advantages of mass production, so that this enterprise can provide all materials to the market at a lower cost than other enterprises or a few enterprises. Then, in this industry, only this enterprise can survive, and other enterprises do not have this viability.