Final answer:
Allocative efficiency is an economic concept regarding efficiency at the social or societal level. It refers to producing the optimal quantity of some output, where the marginal benefit to society of one more unit equals the marginal cost. In a perfectly competitive market, when price equals marginal cost, allocative efficiency is achieved.
Step-by-step explanation:
Allocative efficiency is an economic concept regarding efficiency at the social or societal level. It refers to producing the optimal quantity of some output, the quantity where the marginal benefit to society of one more unit just equals the marginal cost. The rule of profit maximization in a world of perfect competition was for each firm to produce the quantity of output where P = MC, where the price (P) is a measure of how much buyers value the good and the marginal cost (MC) is a measure of what marginal units cost society to produce. Following this rule assures allocative efficiency.
If P > MC, then the marginal benefit to society (as measured by P) is greater than the marginal cost to society of producing additional units, and a greater quantity should be produced. However, in the case of monopoly, price is always greater than marginal cost at the profit-maximizing level of output, as you can see by looking back at Figure 9.6. Thus, consumers do not benefit from a monopoly because it will sell a lower quantity in the market, at a higher price, than would have been the case in a perfectly competitive market.