Perfect Markets and Market Imperfections

The perfect market entails a structure of production and exchange in which optimal outcomes, both private and social, are attained efficiently and simultaneously without the need for intervention by nonmarket actors. In other words, the price and profit signals in the market lead automatically to production efficiency at minimum unit cost and to allocative efficiency at the most desired mix of output. In a perfect market, the self-interested behavior of individuals responding to price signals is sufficient to direct society as it answers the basic questions of what to produce, how to produce, and for whom to produce.

The model of the perfect market rests on the assumption of perfect rationality in the utility and profit maximization motives of economic agents (consumers and producers). Additional assumptions of a perfect market include the voluntary exchange of homogeneous goods and services within complete and perfectly competitive markets under perfect and symmetric information about the prices, quality, and availability of output. These assumptions ensure that no individual market participant can influence market price and that all necessary inputs and possible outputs have a pecuniary value and are traded unconstrained by time or circumstance. In addition, one must assume the absence of several noteworthy features of actual markets, which include externalities, public goods, direct transaction costs, asset specificity, taxes, and other distortions, as well as economies of scale and scope and other resource, political, or technological barriers to entry and exit. In total, the restrictions result in a level of certainty and stability in the market that generate both the full and efficient employment of resources as well as the maximum and correct mix of output by each firm.

However, the assumptions necessary to sustain the model of perfect markets—with its Pareto-optimal levels of production and allocative efficiency, market order, and social coordination—limit its ability to explain or anticipate actual economic processes and events. As such, the perfect market model remains more an abstract theoretical construct that forms an ideal and useful point of reference against which imperfect market structures such as monopoly, oligopoly, and monopolistic competition can be assessed.