First Demand

The Constant-Cost Zucchini Industry

The first step in identifying the long-run industry supply curve for a constant-cost industry is with an increase in demand. Click the [Demand Shift] button to illustrate the shift of the demand curve to D'. Note that with the increase in demand, the market price of zucchinis increases to Pe' and the equilibrium quantity rises to Qe'.

The higher price and larger quantity are achieved as each existing firm in the industry responds to the demand shock. The higher price that buyers are willing to pay induces existing firms to increase their quantities supplied as they move along their individual marginal cost curves. The market, as such, moves along the original market supply curve from one equilibrium point to a higher equilibrium point.

However, the higher price leads to above-normal economic profit for existing firms. And with freedom of entry and exit, economic profit attracts kumquat, cucumber, and carrot producers into this zucchini industry. An increase in the number of firms in the zucchini industry then causes the market supply curve to shift. How far this curve shifts and where it intersects the new demand curve, D', determines that the zucchini market is a constant-cost industry.

The Supply Response

The key for a constant-cost industry is how far the supply curve shifts. For a constant-cost industry the shift matches the shift of the demand curve. As new firms enter the industry, they pay the same resource prices and incur the same higher production cost as existing firms.

Whatever the actual resource price, the end result is that the long-run average cost curve does not change. The minimum efficient scale for a given perfectly competitive firm is the same. This means that they can produce the extra quantity demanded by the zucchini buyers at the same per unit cost that had prevailed.