Which of the following is NOT a characteristic of perfect competition?

In a perfect competition market structure, firms are price takers, meaning they must accept the market price set by the supply and demand because they do not have the power to influence it individually. This characteristic arises from the large number of firms in the market, each producing identical products, which ensures that no single firm can affect the overall market price. Additionally, perfect competition allows for easy entry and exit from the market, enabling new firms to enter when profits are available and exit without barriers when they incur losses.

However, in the long run, firms in a perfectly competitive market will not earn economic profits. Instead, competition drives profits to zero, as any economic profits will attract new entrants, increasing supply until the price falls to the level of average total costs. Therefore, long-run economic profit is not characteristic of perfect competition, making it the correct answer in this context. The essence of perfect competition is that firms can only earn normal profits in the long run, where total revenue equals total costs.