Final answer:
An increase in the money wage rate shifts the aggregate supply curve leftward, causing a decrease in equilibrium real GDP and an increase in the price level.
Step-by-step explanation:
The factor that shifts the aggregate supply curve leftward is the increase in the money wage rate. An increase in potential GDP or real GDP, a fall in the price level, or a decrease in the money price of oil typically implies a shift to the right for the aggregate supply curve. Increased money wage rates can increase the cost of production for businesses, leading to a higher overall price level for the goods and services in the economy (creating inflationary pressure), and this can effectively shift the aggregate supply curve to the left. When the aggregate supply shifts left, the equilibrium real GDP decreases, and the price level increases, representing a contraction in production capacity.