There are following five types (degrees or categories) of price elasticity of supply (PES):
(1) Infinitely Elastic Supply:
When the quantity supplied at the ruling price is infinite, we say the supply is infinitely elastic. An infinitely elastic supply curve is a horizontal straight line as is shown in the diagram 7.1.
In this diagram 7.1, when the price is OP, the producer supplies an infinite amount of goods, if the price falls slightly below OP, then nothing will be supplied by him.
(2) Elastic Supply:
When the percentage change in the quantity of a good supplied is greater than the percentage change in the price of that good, then the supply is said to be elastic supply.
For example, if the price of oranges increases from $5 to $6 and the quantity supplied rises from 150 to 600 oranges, the supply will be elastic.
In the diagram 7.2, SS/supply curve is elastic and the numerical value for elasticity is greater than 1.
(3) Unitary Elasticity of Supply:
When the percentage change in the quantity supplied is exactly equal to percentage change in price that evoked it, the supply is said to have elasticity equal to unity, or the elasticity of supply is equal to 1.
In the diagram 7.3, SS/supply curve drawn through the origin has unit elasticity of supply.
(4) Inelastic Supply:
When the percentage change in the quantity supplied is less than the percentage change in the price that generated it, the supply is said to be inelastic. The inelasticity of supply is less than 1.
In this figure 7.4, SS/supply curve (which is steeper than the elastic supply curve) shows that with a significant change in price, the quantity offered for sale is not very much affected.
(5) Perfectly Inelastic Supply:
In perfectly inelastic supply, the quantity supplied does not change as price changes. The elasticity of supply in other words is zero.
For example, if the price of a painting by an artist who has died, rises from $10 thousand to $50 thousand, the supply of the painting cannot be increased.
Above diagram 7.5, shows the perfectly inelastic supply.