In fact, the only way to induce a change in quantity supplied is with a change in the price. Anything else, everything else, causes a change in supply.

As the supply price induces a change in the quantity supplied and a movement along the supply curve, the five supply determinants (resource prices, production technology, other prices, sellers' expectations, and number of sellers) remain unchanged.

Supply and Quantity Supplied

• Quantity Supplied: Quantity supply is a specific quantity that sellers are willing and able to sell at a specific supply price. It is but ONE point on a supply curve.


• Supply: Supply is the range of quantities that sellers are willing and able to sell at a range of supply prices. It is ALL points that make up a supply curve.

Making Changes

• Change in Quantity Supplied: A change in quantity supplied is a change from one price-quantity pair on an existing supply curve to a new price-quantity pair on the SAME supply curve. In other words, this is a movement along the supply curve. A change in quantity supplied is caused by a change in price.


• Change in Supply: A change in supply is a change in the ENTIRE supply relation. This means changing, moving, and shifting the entire supply curve. The entire set of prices and quantities is changing. In other words, this is a shift of the supply curve. A change in supply is caused by a change in the five supply determinants.

Changing the Quantity

A Change in Quantity Supplied

• A Change in Quantity Supplied: A change in quantity supplied, which is only triggered by a change in supply price, is a movement along the supply curve. Click the [A Price Change] button to demonstrate.


• A Change in Supply: A change in supply, which is triggered by a change in any of the five supply determinants, is a shift of the supply curve. Click the [A Determinant Change] button to demonstrate.

An Important Difference

• First, a supply (or demand) determinant changes.


• Second, this determinant change causes the supply curve (or demand curve) to shift.


• Third, the change in supply (or demand) causes either a shortage or a surplus imbalance in the market. The market is in a temporary state of disequilibrium.


• Fourth, the shortage and surplus imbalance causes the price of the good to change.


• Fifth, the change in price causes a change in quantity supplied (and demanded).


• Sixth, the change in quantity supplied (and demanded) eliminates the shortage or surplus and restores market equilibrium.