Changes in Demand Versus Changes in Quantity Demanded A shift in the demand curve from D₀ to D₁ represents an increase in demand, and consumers will buy more of the product at each price. A shift from D₀ to D₂ reflects a decrease in demand. Movement along D₀ from point a to point c indicates an increase in quantity demanded; this type of movement can only be caused by a change in the price of the product.