A perfectly competitive industry is said to be efficient because the:

• A. government regulates prices to achieve equality
• B. market demand always exceeds market supply
• C. firms can earn long-run economic profits
• D. price equals marginal cost, ensuring resources are allocated to their most valued uses

Answer: (D)

Verified step by step guidance

1. Understand the concept of efficiency in a perfectly competitive market: it occurs when resources are allocated in a way that maximizes total surplus, meaning no one can be made better off without making someone else worse off.
2. Recall that in perfect competition, firms are price takers and produce where price equals marginal cost (P = MC). This condition ensures that the cost of producing an additional unit equals the value consumers place on that unit.
3. Recognize that when P = MC, the quantity produced and consumed is socially optimal, meaning resources are used to produce goods that consumers value most highly, avoiding overproduction or underproduction.
4. Note that government regulation of prices is not necessary in perfect competition because the market naturally drives price to equal marginal cost through the interaction of supply and demand.
5. Understand that in the long run, firms in perfect competition earn zero economic profit, which means resources are efficiently allocated without excess profits or losses, reinforcing the efficiency of the market.