MSCI World Index

Main article: Competition law
The state limits the monopoly market power through anti-trust law, drafting legislation and regulations designed to promote competition in the economy by banning everything that may bring some sort of inefficiency in the market, limiting the market structures are allowed. In all these cases displays its effects before there is finally a monopoly, as it seeks to prevent the development of a structure ultimately inefficient.
However, there are certain cases where the regulation deploys its effects allowing a monopoly, and is limited only to regulate it. If the structure to a more efficient market is a monopoly is, we are faced with a natural monopoly, or economic policies if the state wants to encourage the existence of a monopoly by a company in a specific area, the ideal is to reduce the monopoly power to the minimum at which it is profitable in the market. In this way the state tries to intervening in the market, to alleviate the abuse of market power of monopoly for the benefit of consumers and stakeholders in general.
It is a typical case, for example, of public services because they often involve high fixed costs that create economies of scale that motivate the most efficient solution is to have a single company for the widest possible AMORTIZATION of infrastructure that have been required to development activity (natural monopoly). Other structures which were observed in this regulation may be characterized further, either because it is more profitable to allow the existence of market power, as in monopolistic competition, or when it can not be bound to perform another behavior, such as of implicit collusion. In these cases what the law is to equate the situation of the consumer to the monopolist, so that this provides a greater amount of the producer and a lower price.
Finally we found the cases of state monopoly, where the state decides to create a monopoly in an area it considers its strategic (monopoly artificial). In this case the regulation is continuous, as the state entity that makes all decisions for political reasons.