The divergence between the economic and legal concepts of monopoly and the consequences thereof have been emphasized by various writers in recent years. Monopoly in economics means control of the market; that is, the ability of a seller by increasing or decreasing his output to affect the price of the product sold. Moreover, monopoly is recognized as being a matter of degree, depending upon the number of buyers and sellers of a commodity and the availability of adequate substitutes, ranging from pure monopoly through duopoly, oligopoly and monopolistic competition. By contrast, as Professor Mason has pointed out, "The term monopoly as used in the law is not a tool of analysis but a standard of evaluation," by means of which public policy with respect to certain business practices might be developed. In law monopoly has largely meant the suppression of the freedom of an individual or firm to compete, by legal restraint, by agreement among competitors or by predatory tactics of rivals.
Robert W. Harbeson,
A NEW PHASE OF THE ANTITRUST LAW,
Mich. L. Rev.
Available at: https://repository.law.umich.edu/mlr/vol45/iss8/3