Elasticity

What Is Elasticity?

Elasticity is a way of measuring sensitivity. It shows how strongly one quantity reacts when another quantity changes. Because it is expressed as a ratio of percentage changes rather than raw amounts, it can be compared across products, markets, and time periods that use different units. The most widely discussed form is price elasticity of demand, which measures how much the quantity of a product people buy changes when its price changes. Other forms include income elasticity of demand, which looks at how purchases respond to changes in household income, and cross-price elasticity, which measures how demand for one good responds to a change in the price of another.

How Elasticity Is Calculated

For price elasticity of demand, the basic formula is:

Elasticity = percentage change in quantity demanded ÷ percentage change in price

Because demand usually falls when price rises, the result is typically negative. Analysts often ignore the sign and focus on the size. A value with an absolute size above 1 is called elastic, meaning quantity responds strongly to price. A value below 1 is inelastic, meaning quantity responds weakly. A value of exactly 1 is unit elastic.

For illustration only: if a price rises by 10 percent and quantity sold falls by 20 percent, the elasticity is -2, which is elastic.

Why It Matters to Investors

Elasticity helps explain how a company's revenue responds to pricing decisions. When demand is inelastic, a price increase can raise total revenue even as sales volume falls, which is one reason businesses selling necessities may have more room to raise prices. When demand is elastic, price cuts can attract enough extra buyers to increase revenue. Investors who read company filings or industry reports often use these ideas to judge how resilient a firm's sales may be during price changes or economic slowdowns.

Elasticity is an estimate, not a fixed property. It can change over time, differ across customer groups, and depend on the availability of substitute goods, so it is best treated as one input among many rather than a precise forecast.