When both the demand and supply curves shift to indicate an increase in demand and supply in the same proportion. Then:
When both the demand and supply curves shift to indicate an increase in demand and supply in the same proportion. Then:
Solution
Option 1 -> Incomplete statement as it doesn't specify what happens to equilibrium quantity.
Option 2 -> Incorrect. When both curves shift proportionally, quantity changes significantly.
Option 3 -> Incorrect. While price remains unchanged, quantity should increase, not decrease.
Option 4 -> When demand increases, it puts upward pressure on price and increases quantity. When supply increases, it puts downward pressure on price and increases quantity. If both shift in the same proportion, the price effects cancel out (leaving price unchanged), while the quantity effects reinforce each other (increasing quantity).
Hence, Option 4: Equilibrium price remains unchanged but equilibrium quantity increases -> When both demand and supply increase proportionally, the upward pressure on price from demand increase is exactly offset by the downward pressure from supply increase, keeping price constant. However, both shifts work in the same direction for quantity - demand shift increases quantity demanded and supply shift increases quantity supplied - resulting in a higher equilibrium quantity at the same price level -> correct
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