Supply Elasticity

Suppliers profit by selling goods and services at higher prices than their cost to produce. The amount of profit is determined by the cost of the factors of production to produce the product and on the suppliers' efficiency in producing the product. Since higher prices facilitate earning a profit, and since the amount of profit is also dependent on the quantity sold, if increased demand raises prices, then suppliers will respond by increasing their supply, since that will allow them to earn a higher profit. Of course, this is merely the law of supply, but it does not state how much supply will change when prices change. The elasticity of supply measures the percentage change in the quantity of supply compared to the percentage change in a supply determinant, much like how the elasticity of demand is measured. Although the elasticity of supply can be measured against several supply determinants, the most important is the price. The price elasticity of supply measures the percentage change in supply quantity compared to the percentage change in the price, which, in turn, determines the change in total revenue.

Supply Quantity Change %
Price = ÷
Elasticity Price Change %

The price elasticity of supply varies widely, depending not only on the product or service, but also on whether the price change occurs over a short time or a long time. If the supply changes little with a change in price, then supplies are considered inelastic. Supply is elastic if there are large changes in supply for a small change in price. If the percentage change in price is equal, though opposite, to the percentage change in quantity, then supply elasticity is unit elastic.

For instance, the supply of land is generally inelastic, because, as Will Rogers once quipped, they're not making any more of the stuff. By contrast, the supply of software is almost perfectly elastic since it costs little to make and distribute copies of software.

Graphs of Perfectly Elastic and Perfectly Inelastic Supply

2 graphs of a perfectly elastic supply curve and a perfectly inelastic supply curve.

Perfectly Elastic Supply (Graph #1):

  • Elasticity = ∞.
  • Suppliers will supply any amount above price Pe.
  • At Pe, the market supply equals the quantity demanded.
  • No supplier wants to supply its product for less than Pe.
  • A perfectly elastic supply can be best illustrated by a drug company selling a cancer drug that cures cancer. The drug company will sell it at the highest price that the market will bear, but it will supply any amount at that price. Higher prices would make the drug unaffordable.

Perfectly Inelastic Supply (Graph #2):

  • Elasticity = 0
  • At quantity Qi, the amount supplied is what the market demands, whatever that is, regardless of the price.
  • The best real-world example of perfectly inelastic supply is land, since suppliers can only sell what they have — they cannot create more, regardless of the price, although a higher price would induce more landowners to sell.
Elasticity of Supply
If supply elasticity < 1 then supply is inelastic
= 1 unit elastic
> 1 elastic

The price elasticity of supply varies over the supply curve for most goods or services, because production often involves several different methods of increasing the supply. For instance, when the price increases, suppliers can increase the use of their available resources and they can hire more labor over the short term. Suppliers may also be able to shift resources from less profitable to more profitable products. However, if the price continues to rise, then suppliers must make major investments to continue increasing the supply, so the price elasticity of supply is elastic at first, when suppliers can put idled resources to work, then becomes more inelastic over the short term as prices continue to rise, not only because suppliers must make major investments, but it would take time for new suppliers to enter the market. Likewise, if prices fall, suppliers can idle resources and lay off their workers, but suppliers tend to maintain a minimum supply to cover fixed costs. However, as prices continue to drop, then eventually suppliers will sell their factors of production, or suppliers will leave the industry to find better opportunities elsewhere.

For example, if a farmer brings a truckload of watermelons to the farmers market, then he will try to sell all the watermelons, regardless of the price; otherwise, the watermelons will perish. On the other hand, even if the price is very high, the farmer has no way of supplying more watermelons right away.

Over the short run, supply tends to be in inelastic, because of the limited options available to change supply. Over the long-run, supply becomes more elastic, because suppliers can take actions that take more time to increase the supply, such as building new factories, or growing more of a certain crop on farmland.

How Prices Change With Demand Under Inelastic and Elastic Supply

Diagrams showing how demand changes prices when supply is inelastic compared to when supply is elastic.

Inelastic Supply (Graph #1):

  • When demand changes from D1 to D2, the percentage change in price exceeds the percentage change in quantity provided.

Elastic Supply (Graph #2):

  • When supply is elastic, then the percentage change in quantity exceeds the percentage change in price.