Final answer:
The statement is true because, in the long-run equilibrium of a perfectly competitive market with firms having identical costs, economic profits are zero, leading firms to operate at an efficient scale where they minimize average total costs and price equals marginal cost.
Step-by-step explanation:
The statement that the long-run equilibrium in a competitive market characterized by firms with identical costs is generally characterized by firms operating at efficient scale is true. In the context of perfect competition, the process unfolds where firms will enter the market if they see positive economic profits, and leave or scale down if they are experiencing losses. Over time, this entry and exit of firms will drive economic profits to zero, and the market will reach a long-run equilibrium. This long-run equilibrium is characterized by firms producing at the point where average total costs are minimized, which is the point of efficient scale, and they earn zero economic profits. Additionally, the price in the market will be equal to the marginal cost, which ensures that both allocative and productive efficiency are achieved.
At this stage, no new firms are incentivized to enter the market, and existing firms do not have an incentive to leave, as long as the market conditions remain constant. This outcome meets both the conditions of allocative efficiency (where price equals marginal cost) and productive efficiency (where firms operate at the lowest average total cost).