What is Change in Quantity Supplied?

Change in quantity supplied occurs when the quantity supplied of a commodity changes due to a change in its price while the other factors remain constant. It is represented graphically as a movement along the same supply curve. There are two cases of movement along the same supply curve. It may be either,

1. Expansion of Supply (An Upward Movement)
2. Contraction of Supply (A Downward Movement)

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. When there is a contraction in the quantity supplied of a commodity because of a fall in the respective price by keeping other factors constant, it is known as a Contraction of Supply. The contraction in supply results in a downward movement along the same supply curve.

The terms Change in Quantity Supplied and Change in Supply are usually used interchangeably but are different from various prospects. Change in quantity supplied is defined as the change in the level of the quantity that the seller wishes to sell at a particular price, occurring due to a change in the price of the commodity (other factors remaining constant). Change in supply is defined as the change in the level of the quantity that the seller wishes to sell at a particular price, occurring due to changes in other factors of the supply (own price of the commodity remains the same).