What conditions are necessary for a market to be perfectly competitive?

When economists analyze the production decisions of a firm, they take into account the structure of the market in which the firm is operating. The structure of the market is determined by four different market characteristics: the number and size of the firms in the market, the ease with which firms may enter and exit the market, the degree to which firms' products are differentiated, and the amount of information available to both buyers and sellers regarding prices, product characteristics, and production techniques.

Four characteristics or conditions must be present for a perfectly competitive market structure to exist. First, there must be many firms in the market, none of which is large in terms of its sales. Second, firms should be able to enter and exit the market easily. Third, each firm in the market produces and sells a nondifferentiated or homogeneous product. Fourth, all firms and consumers in the market have complete information about prices, product qua