Chapter 14: Firms in Competitive Markets

In such environments, firms function as price takers, meaning their revenue derives directly from multiplying their output quantity by the externally determined market price. A fundamental principle governing firm behavior is that both average revenue and marginal revenue equal the prevailing market price. To achieve profit maximization, firms should expand production up to the point where marginal revenue equals marginal cost, a decision rule that applies across all market structures. The marginal cost curve above the average variable cost threshold forms the foundation of a firm's short-run supply curve, while the portion of the marginal cost curve exceeding average total cost determines its long-run supply behavior. In the short run, firms must decide whether to continue operating or temporarily shut down production; this decision hinges on comparing price to average variable cost, since fixed costs are sunk expenses irrelevant to immediate production decisions. The chapter illustrates these concepts through practical scenarios, such as restaurants evaluating whether to remain open during slow business periods based on variable operating expenses. Over longer time horizons, the freedom for businesses to enter or leave the market drives competitive outcomes toward equilibrium, where economic profits diminish to zero as firms operate at their efficient scale. At this point, price converges with both marginal cost and minimum average total cost, producing an allocation of resources that maximizes total surplus. When demand conditions shift upward, the short-run response involves higher prices and elevated profits that attract new market participants. Entry continues until prices decline and return to minimum average total cost, resulting in expanded market output distributed across a larger number of firms. The chapter acknowledges scenarios where long-run supply curves slope upward rather than remaining perfectly elastic, which occurs when certain productive resources are limited or when production costs vary significantly among firms. Ultimately, the competitive mechanism ensures that firms' pursuit of profit aligns with broader economic efficiency and consumer welfare objectives.