Final answer:
The short-run aggregate supply curve shifts when nominal wages and other input prices change, which affects the cost of production. This can lead to shifts in the curve to the right (decreased input prices) or to the left (increased input prices), but changes in the aggregate demand only affect movement along the curve, not its position.
Step-by-step explanation:
The question asks about the factors that cause a shift in the short-run aggregate supply curve. Other things equal, the short-run aggregate supply curve shifts its position when nominal wages and other input prices change. A change in the rate of inflation, price level, or aggregate demand does not shift the short-run aggregate supply curve; rather, these factors cause movement along the curve. The key reason behind a shift in the AS curve is the change in production costs, such as wages for labor, which are a component of input prices.
When input prices decrease, the short-run aggregate supply curve shifts to the right, indicating an increase in the total production at every price level. This is because products can be produced at a lower cost, leading to higher profit margins for the same prices. Conversely, an increase in input prices results in a leftward shift, signifying a decrease in production at every price level. Changes in aggregate demand influence the equilibrium price and output levels but do not directly cause the supply curve to shift.