B I U E 4 = KEY CONCEPTS Change in supply occurs when something prompts producers to offer different amounts for sale at every price. When production costs increase, supply decreases; when production costs decrease, supply increases. Just like change in demand, change in supply actually shifts the supply curve. Six factors cause a change in supply: input costs, labor productivity, technology, government actions, producer expectations, and number of producers. 1. When does a change in supply occur? 2. How does a change in supply different from a change in quantity supplied