Final answer:
A change in aggregate quantity supplied is a movement along the existing supply curve due to price level changes, whereas a change in aggregate supply is a shift of the entire supply curve caused by non-price factors such as productivity growth or input prices. A rightward shift indicates increased efficiency and output at the same cost, and a leftward shift signifies increased production costs and reduced output.
Step-by-step explanation:
The difference between a change in aggregate quantity supplied and a change in aggregate supply is found in the underlying reasons for the shifts in the supply curve. A change in aggregate quantity supplied refers to a movement along the existing aggregate supply curve, which occurs in response to a change in the price level. This is represented graphically as a movement from one point to another along the same curve. In contrast, a change in aggregate supply refers to a shift of the entire supply curve, which can be caused by factors other than price changes, such as productivity growth or changes in input prices.
When productivity growth occurs, it results in a more efficient production process. This leads to a higher output at the same cost or the same output at a lower cost, effectively shifting the aggregate supply curve to the right. Conversely, an increase in input prices would raise production costs, leading to a leftward shift of the aggregate supply curve as producers supply less at every price level.
For example, in the supply of milk, a change in quantity supplied would occur if milk's price increased, leading producers to move up along the existing supply curve, supplying more milk. However, if advancements in dairy farming technology (productivity growth) were made, or if the cost of cattle feed (input price) changed significantly, this would cause the entire supply curve for milk to shift, representing a change in the milk's aggregate supply.