완벽 경쟁의 장기 공급 곡선

In perfect competition, the long-run supply curve is perfectly elastic because firms can adjust their scale of production and all inputs become variable. Since all firms have identical production functions and face identical input prices, they all operate at the same minimum average total cost. Firms willingly supply any quantity at the market price covering their costs, creating a horizontal supply curve.

A horizontal long-run supply curve means firms will supply any quantity of output at a constant price equal to their minimum average total cost. This occurs in constant-cost industries where input prices remain stable as firms enter or exit the market. The flat curve reflects that production costs per unit do not change with industry expansion or contraction.

In the long run, firms maximize profits by producing where marginal cost equals the market price. Since all firms in perfect competition have identical production functions and input costs, they all reach the same minimum average total cost point. This ensures efficient production at the lowest possible cost per unit across the entire market.

A constant-cost industry maintains stable input resource prices even as firms enter or exit the market. This stability ensures the long-run supply curve remains perfectly elastic and horizontal. Without constant costs, input prices would rise or fall with industry changes, causing the supply curve to slope upward or downward instead.

The short-run supply curve slopes upward because firms cannot adjust all inputs, while the long-run supply curve is perfectly elastic and horizontal. In the long run, firms can vary all inputs and scale production, allowing them to operate at minimum average total cost. This flexibility creates the flat supply curve characteristic of long-run equilibrium in perfect competition.

No, individual firms cannot influence the market price in perfect competition because numerous firms produce identical products. Each firm is a price taker, accepting the prevailing market price determined by overall supply and demand. Firms can only choose their production quantity, not the price at which they sell.

When input costs change, the long-run supply curve shifts because firms' minimum average total cost changes. In increasing and decreasing cost industries, the supply curve slopes upward or downward rather than remaining horizontal. The constant-cost assumption ensures stable input prices, maintaining the perfectly elastic supply curve characteristic of long-run equilibrium.