Generally speaking, a free market is a contestable market with free entry. That is, a market where buyers and sellers are free to agree their exchanges without any undue interference on demand and supply.
To understand the importance of free entry let us imagine a remote small island community with a single store. Its population is not enough to sustain two stores and as expected the existing store is a natural monopoly. If one of the inhabitants decides to challenge the incumbent monopolist and opens a new store both will run their stores at a loss until one of them eventually is ruined and gives up.
While the two stores remain competing the islanders benefit from greater supply at a lower price, but once the monopoly is re-established they face reduced supply and higher prices so that the surviving store can recover the losses incurred while competing with the other store. Meanwhile, during the competitive period the two store owners engaged in both fair and unfair tactics to gain or keep market share through better customer service, credit terms, product quality, etc. Some of these sales tactics are considered beneficial while others disrupt the traditional rules of civility and trust in the community. Therefore, the islanders’ ruler received many requests to stop them or to let them fight to the end. Which are his options?
He can uphold the laisser-faire principle of no interference to ensure an absolute right to free entry. Alternatively, he may introduce a licensing system to grant the monopoly on a temporary or permanent basis. Both options could be improved to retain the benefits of competition and minimize its costs. For instance, he could ban unfair sales tactics or he could auction periodically the store license. These two options should be carefully assessed to determine which would be the most efficient in a Pareto sense. That is, which would allow competition to generate greater benefits.
This example is not a simple curiosity in remote societies. Indeed, we find many similar situations in developed countries. For instance, licensing is very common in public transport, pharmacies, funerary services, roads and other infrastructures, healthcare, telecommunications, etc. And, such licensing while often done under the guise of consumer protection is in fact used to regulate or limit competition.
In fact, free markets are only a foundation of capitalism as long as they contribute to enhance fair competition, that is to create competitive markets where prices are established in accordance with supply and demand.
The simplest form of a competitive market is a market without entry barriers and where there are many suppliers and buyers so that all parties are price-takers. But, this is not always required. For instance, Stanley Jevons (1871) one of the founders of the marginal utility theory of value, considered that a market could be made of only two counterparties.
Although one may idealize market structures that create a system of perfect competition, capitalism does not need such a stringent form of competition. Some imperfections or regulations are tolerable or even desirable to achieve what Churchill (1909) called the need for competition upward but not downward (e.g. competition that could drive labor into slavery or tax rates to zero).
Such departures from an idealized world of perfect competition may be more or less extensive depending on the nature of the market, e.g. largest in labor markets than in capital or in goods and services markets. Even among the latest one must distinguish between markets with prohibitive carrying costs (e.g. fish markets) and speculative markets where carrying costs are negligible. The second factor to bear in mind is whether the so-called market failures and divergences between private and social optimization are significant and susceptible of correction without secondary damages.
In modern capitalism the most relevant issue is whether monopolistic and oligopolistic markets still can be considered competitive. For instance, does the fact that the Coca-cola and Pepsico share of the soft drinks market has risen from about 50% in the 1960s to the current level of around 70% means that such market is no longer considered as competitive? Of course not, because there is no entry barriers in such market and in fact there are many small producers competing with these two giant firms. However, if their dominance had been achieved or preserved through licensing or any other form of government favoritism then we should not consider such market as competitive.
Currently, there is a market – the market for corporate control - whose freedom is essential to preserve because of the growing separation between ownership and control. In most big firms the degree of capital dispersion is sufficiently large to facilitate collusion between managers and a small group of shareholders who introduce many obstacles (e.g. poison pills) to prevent others from challenging their power within the firm and to seclude them from hostile takeovers. Moreover, invoking the risk of short-termism and the speculative nature of such markets these groups of insiders often succeed in persuading politicians to enact legislation to obstruct the development of markets for corporate control which are indispensable to protect minority shareholders.
In general, the risk of collusion between sellers is the same whether the oligopolies exist in regulated or non-regulated industries. As Adam Smith reminded us long ago “people of the same trade seldom meet together, even for merriment and diversion, but the conversation ends in a conspiracy against the public, or in some contrivance to raise prices”. It also common to find businessmen who were enthusiastic free-market supports when they were challenging the incumbents but transform overnight into the most determined protectionists once they join the incumbents.
In fact, this is the reason why capitalists are not always among the main supporters of capitalism and free markets. Only consumers remain always beneficiaries with the greatest interest in free markets. This is the reason why some argue that, if it was not for Marx, capitalism would be better named as consumerism.
However, consumers are frequently too numerous to organize conspiracies or to simply oppose those of the sellers. That is the reason why, in the end, the existence of free competitive markets depends on the rule of law and governments prohibiting or limiting non-competitive practices.