Difference Between Expansion of Supply and Increase in Supply

Expansion of Supply and Increase in Supply often seem similar but are different from one another. Expansion of Supply is defined as an increase in quantity the seller wishes to sell when there is a rise in own price of the commodity. Whereas, an Increase in Supply is defined as an increase in quantity the seller wishes to sell due to changes in other factors, other than own price of the commodity.

Expansion of Supply leads to an upward shift in the supply curve, while Increase in Supply leads to a rightward shift of the supply curve.

What is Expansion in Supply?

When there is an expansion in the quantity supplied of a commodity because of a rise in own price of the commodity, by keeping other factors constant, it is known as an Expansion of Supply. It results in an upward movement along the same supply curve. It is also known as an Extension in Supply.

Price (₹)	Quantity (in units)
10	150
15	250

Here, at ₹10, the seller is willing to sell 150 units of goods; however, at ₹15, the seller is willing to sell 250 units of goods. This scenario shows that the rise in prices of the goods will leads to expansion in quantity supplied (other factors remain constant); i.e., Expansion of Supply.

Here, S is the initial supply curve showing the relationship between quantity supplied and price of the commodity. Quantity supplied is show on the Y-axis and Price is shown on the X-axis. When the price rises from ₹10 to ₹15, the quantity supplied expands from 150 units to 250 units (also known as the expansion of supply), which results in an upward movement from A to B along the same supply curve SS.

What is Increase in Supply?

An increase in the supply of a commodity due to factors other than the own price of the commodity is known as an Increase in Supply. In simple terms, the supply for a commodity increases at the same price, because of changes in other factors, other than own price of the commodity. An increase in supply results in a rightward shift in the supply curve.

Price (₹)	Quantity (in units)
15	50
15	75

Here, at ₹15, initially the seller is willing to sell 50 units; however, at the same price of ₹15, the seller is willing to sell 75 units of commodity. This increase in supply is caused by changes in other factors of supply, other than own price of the commodity.

Here, quantity supplied is shown on the X-axis and price is shown on the Y-axis. S₁S₁ is the initial supply curve showing 50 units of quantity supplied at ₹15. Increase in supply from 50 units to 75 units at the same price of ₹15, causes a rightward shift in the supply curve from S₁S₁ to S₂S₂.

Difference Between Expansion of Supply and Increase in Supply

Basis	Expansion of Supply	Increase in Supply
Meaning	An increase in quantity supplied due to an increase in price while all other factors remain constant is known as Expansion of Supply.	An increase in the supply of a commodity due to factors other than the own price of the commodity is known as an Increase in Supply.
Effect on Supply Curve	It results in an upward movement in the same supply curve.	It results in a shift in the supply curve in the rightward direction.
Reason	It happens due to an increase in the price of the given commodity.	It occurs as a result of other factors, such as an increase in the price of substitute and complementary goods, an increase in income levels, etc.