In this structure of market competition between the consumers exists. The firm produces a product for which it does not exist substitute next. It has presence of barriers to the entrance of new firms, that is, it is necessary to keep the competitors in potential moved away. These obstacles can be managed by the monopolista through: ) Control on the supply of the substance cousin; b) Legal barriers as registers of patents; c) Governmental licenses and concessions and others. It is important to stand out that, in many circumstances, it is the structure most appropriate for the production of certain goods and services as in the governmental monopolies (Post offices, CESAN).
The legislation of the majority of the countries forbids the monopoly, with exception exerted them by the State, generally in strategical products and services. The monopoly ' ' puro' ' it is a theoretical construction, because, in the practical one, it does not exist. The hypotheses of the model are: ) the pure monopoly or natura, due to high scale of required production, demanding upstream raised one of investments. The monopolista company already this established in great dimensions and has conditions to operate with low costs. Some company very becomes difficult to obtain to offer to the product to a price equivalent to the monopolista firm; b) protection of patents (right only to produce the good). Example: photocopy; c) control on the supply of substance-cousin-keys.
Example: The Alcoa withheld almost all the bauxite mines in U.S.A. (raw material of aluminum). d) tradition in the market. Example: market of clocks: the Japanese had needed to invest much money, during much time, to concur with the tradition of the Swiss clocks. An implicit hypothesis in the behavior of the monopolista is that it does not believe that the high profits that the short-term one gets they can attract competitors, or that the high prices can drive away the consumers; that is, it believes that, exactly in the long run, it will remain as monopolista.