The long-run average cost curve is determined by the technology of production and by resource prices. For example, if there is a change in technology that increases the degree of returns to scale to the firm, the long-run average cost curve shifts downward. Similarly, if the entry of firms into an industry causes resource prices to rise, the long-run average cost curve shifts upward. In the first case, some of the short-run average total cost curves shift downward (because of increasing returns to scale). In the second case, all short-run average total cost curves shift upward.