However, other relations can also be thought of as elastic. For example, demand might be elastic relative to income. In this case, relatively small changes in income can trigger relatively large changes in demand.

Demand and Supply

• Demand: Elastic demand exists if relatively small changes in price cause relatively large changes in quantity demanded. Elastic demand means that changes in the quantity demanded are relatively responsive to changes in the price. An elastic demand has a coefficient of elasticity greater than one (with the negative value ignored).


• Supply: Elastic supply exists if relatively small changes in price cause relatively large changes in quantity supplied. Elastic supply means that changes in the quantity supplied are relatively responsive to changes in the price. An elastic supply also has a coefficient of elasticity greater than one.

Perfect and Relative

• Perfectly Elastic: Perfectly elastic means an infinitesimally small change in price results in an infinitely large change in quantity demanded or supplied. This elasticity alternative exists when the price is fixed, that is, an infinite range of quantities is associated with the same price. This is the extreme, limiting case of elastic. Perfectly elastic demand can occur, in theory, when buyers have the choice among a large number of perfect substitutes-in-consumption. In an analogous way, perfectly elastic supply can occur when producers have the ability to switch resources among a large number of perfect substitutes-in-production.


• Relatively Elastic: Relatively elastic means that relatively small changes in price cause relatively larger changes in quantity. Quantity is very responsive to price, but not infinitely so. The percentage change in quantity is greater than the percentage change in price. Relatively elastic demand occurs when buyers have the choice among a large number of close but not perfect substitutes-in-consumption. In an analogous way, relatively elastic supply occurs when producers have the ability to switch resources among a large number of close but not perfect substitutes-in-production.