Movement along the Demand Curve and Shift of the Demand Curve - Change in Quantity Demanded: Movement along the Demand Curve

When people buy more or less of something only because its price changes (and nothing else changes), it is called a change in quantity demanded.

1. Expansion of Demand: If price goes down, people buy more units—this is called expansion.
2. Contraction of Demand: If price goes up, people buy fewer units—this is contraction.

When price falls from ₹100 to ₹90, demand rises from 1 kg to 2 kg—an expansion of demand.

When price rises from ₹70 to ₹80, demand falls from 6 kg to 4 kg—a contraction of demand.

• The downward movement from a higher point to a lower point on the curve is expansion (buying more at a lower price).
• The upward movement from a lower point to a higher point is contraction (buying less at a higher price).

Think of a local market sale: If mangoes become cheaper, customers buy more. If they get expensive, people buy less.

• Expansion: Price falls, and quantity demanded rises (down the demand curve).
• Contraction: Price rises, quantity demanded falls (up the demand curve).
• Movement along the demand curve shows changes in quantity demanded due to price, not because of other reasons like income or preferences.