The modern economic system is a complex structure. It consists of many information, commercial, industrial, financial institutions that interact on the basis of legal norms and are united by a single concept of "market". 
General characteristics of the system
The market is presented as an organized structure in which there are consumers and producers, buyers and sellers, where during supply and demand interactions sales volumes and product prices are formed. During the consideration of the institute, the number of entities involved in the exchange of money for any products is of paramount importance.
Key element
The essence of market relations is expressed by competition. It represents the central link in all relations relating to trade. Competition acts as a form of rivalry between participating entities. It is due to the sovereign right of each business entity to realize their economic potential, which, in turn, inevitably leads to their collision. Thus, the achievement of the goals facing the manufacturer is carried out by infringing upon the interests of other entities.
Market in the face of imperfect competition
Such rivalry between business entities has always existed. However, the peak of its development occurs at the end of the 19th - beginning of the 20th century. The main determining factor was the emergence of monopolies. At that time, there was a concentration of capital, joint-stock companies arose, and control over financial, material, and natural resources intensified. Monopolization was a natural consequence of the jump in the dynamics of industrial production under the influence of scientific and technical progress. In the late 19th and early 20th centuries, free trade was glorified in the works of many figures. At the same time, concepts such as “free” - “perfect” and “monopoly” - “imperfection”, “social injustice” were identified.
The latter was interpreted as the inefficiency of the system that appeared as a result of violations in the mechanism for equalizing profits. Social imperfection was manifested in the fact that monopolists took part of the income from other industries. Over time, the concept has lost its economic meaning. This was due to the fact that representatives of the theory of imperfect competition markets began to consider monopoly as a condition for mass production. It should have been accompanied by increased productivity and lower costs. Imperfection was recognized only socially. It manifested itself in relation to non-monopolized producers. 
Current conditions
Today, imperfect competition markets exist mainly in monopolized sectors. Their appearance is due to two reasons. First of all, there is a tendency towards a decrease in the number of sellers in those sectors that are characterized by large savings and reduced costs. Large firms in the market of imperfect competition spend less on production. This, in turn, allows them to sell products at lower prices than small enterprises. As a result, the latter are driven out of the industry. Imperfect competition markets also appear when there are certain difficulties with the entry of new producers into the industry. Obstacles can arise from stringent government regulations that limit the number of companies.In addition, entry into the industry may be too expensive for new manufacturers.
Key features
Features of the imperfect competition market are as follows:
- There are two or more sellers who have a certain (limited) control over pricing, compete with each other.
- At least one sign of perfect competition is not respected.
- Sellers or buyers take into account the ability to influence price formation.
Types of markets imperfect competition
For a better understanding and a more thorough study of the mechanism, it is necessary to consider the existing classification of structures. The following types of imperfect competition markets are:
- Pure monopoly.
- Oligopoly.
- Duopoly.
- Monopolistic competition with product differentiation.
In modern conditions, only markets of imperfect competition or free trade cannot exist. Today, there is a mixture of elements of different structures.
Pure monopoly
It is an abstraction, a situation that is practically impossible in reality. Nevertheless, in a number of sectors there are markets for imperfect competition, close to a pure monopoly. In a broad sense, it is such an organization scheme in which the number of sellers becomes so small that each of them can no longer affect the total volume of the offer and, accordingly, the price of the product. In narrow consideration, a monopoly is a company that has no competitors.
However, it is impossible to find an enterprise whose product demand curve is absolutely inelastic. This means that when using the concept of "monopoly", especially in its pure form, there is always a certain proportion of conventionality. In this structure, there is one seller of the product that does not have substitutes (substitutes for goods). The monopolist seller is involved only in interactions with buyers of products. Such relationships have their own specifics. It consists in the fact that if the monopolist reduces the cost of production, then the consumer will acquire more. 
Natural Monopolies
Such imperfect competition markets span rare products, industries, and industries. Natural monopolies are formed around such objects, regarding which rivalry is unacceptable. These include, in particular:
- The railway.
- Defense complex.
- Some types of energy and transport.
According to Stanlake, rivalry between enterprises of these industries can only lead to duplication of costs for expensive equipment used in the main production. In this regard, it is necessary to form natural monopolies. For this market model of imperfect competition, the following are characteristic:
- Long-term economies of scale due to technological factors.
- Unprofitable marginal price formation.
- The presence in the industry of 1-2 large (profitable) companies.
- The probable existence of other enterprises, which will nevertheless be unprofitable in the long run.
- Profitable unregulated pricing of large companies above average and marginal costs.
State control
The need to provide monopoly (exclusive) rights to supply consumers with resources or to service a certain territory or the whole country requires state regulation and supervision. This is necessary to eliminate the abuse of power in the market and undesirable consequences for users.
Oligopoly
It is a system in which a small number of companies producing products and acting together are present. The peculiarity of the oligopoly is that there are not so many entities and they can influence the market individually. The simplest form is duopoly. It assumes the presence on the market of two manufacturers of specific products.Moreover, each of them can satisfy independently and fully solvent demand. Oligopoly can be of the first or second type. Form 1 is noted in industries with absolutely uniform goods and large companies. A 2nd type oligopoly takes place when several entities sell a differentiated product. For example, this is noted in the automotive industry. 
Monopoly with product differentiation
Such a system can be presented as a competition for several sellers selling very similar products. Typically, this is a group of specialty products. Differentiation in this case is the lack of uniformity of services and goods. The manufacturer is trying to make creating his product somewhat different from the others in order to sell it at a higher cost. Differentiation, as a rule, does not occur relative to the main purpose of the product, but through various attempts by the seller to form the idea that it is his products that carry more utility than those produced by competitors.
Monopsony
All that is said above refers to the monopoly of the manufacturer. Monopsony is a system in which many enterprises produce a product (factor of production) for one customer. For example, the state acquires weapons in different countries. The buyer in monopsony has great power over prices. He sets the purchase price, which all manufacturers are guided by.
The bid price will reflect the dynamics of the average costs of the entire industry. It can be either rising or falling. It follows that the additional (marginal) costs product acquisitions will no longer be unchanged. They can also be either rising or falling.
Service sector
It is quite natural that in modern conditions there is imperfect competition on labor market. Moreover, as experts say, free circulation is more likely an exception to the general rule. The extreme state of the structure is the monopsony mentioned above. In this form, imperfect competition in the labor market may exist in small cities in which one enterprise is almost the only employer. Due to the fact that within the framework of monopsony, the employer represents a significant share of the demand for services, he dictates the salary rate. She, in turn, directly depends on the number of people employed.
Unlike an enterprise operating in conditions of perfect competition, the monopsonist is characterized by an ascending line of supply. The company will be forced to set high salaries to attract more employees. In other words, marginal cost to the enterprise will exceed the cost of the resource. The cost of an additional employee will exceed his salary by the amount necessary to bring the salary of previously hired personnel to a new level. The newly accepted rate should be paid to all previously attracted employees, and to a new specialist. If you graphically depict this process, then the line of marginal costs will go higher than the supply curve.
