Changes in Equilibrium In panel (a), a rise in aggregate income causes the demand for pizza to increase: at any given price, consumers now want to buy more pizza. This is represented by a rightward shift in the demand curve from D₁ to D₂. The market moves to the new intersection of supply and demand. The equilibrium price rises from P₁ to P₂, and the equilibrium quantity of pizza rises from Q₁ to Q₂. In panel (b), a rise in the price of materials decreases the supply of pizza: at any given price, pizzerias find that the sale of pizza is less profitable and therefore choose to produce less pizza. This is represented by a leftward shift in the supply curve from S₁ to S₂. The market moves to the new intersection of supply and demand. The equilibrium price rises from P₁ to P₂, and the equilibrium quantity falls from Q₁ to Q₂.