Elasticity (economics)

In economics, elasticity is a mathematical tool used to measure responsiveness. It quantifies how much one economic variable changes when another variable changes. For example, it can show how much the quantity of a good demanded changes when its price moves. This concept helps economists understand the behavior of both buyers and sellers. By using elasticity, researchers can predict how people and companies might react to different economic shifts.

To calculate elasticity, economists use a specific ratio. They divide the percentage change in one variable by the percentage change in the other variable. This ratio is unitless, meaning it does not depend on the specific units being measured. There are three main ways to categorize the result. An elastic variable has an absolute value greater than 1. This means it responds more than proportionally to a change. A unit elastic variable has a value equal to 1, responding proportionally. Finally, an inelastic variable has a value less than 1, meaning it changes less than proportionally.

There are several distinct types of elasticity used in economic theory. Price elasticity of demand measures how sensitive buyers are to a change in a product's own price. Price elasticity of supply measures how much the quantity supplied by producers changes when prices change. Income elasticity of demand shows how demand responds to changes in consumer income. Cross-price elasticity of demand measures how the price of one good affects the demand for a different good. There is also elasticity of scale, which looks at how output changes relative to inputs in production.

The history of this concept traces back to the late 19th century. Alfred Marshall first cited price elasticity in an informal way in 1890. He introduced it in his influential book, Principles of Economics.

Later, the concept underwent deeper study in the United States. In the late 1960s, Joshua Levy and Trevor Pollock conducted a major study. They analyzed the price elasticity of both supply and demand for various US products. This work helped solidify elasticity as a core part of neoclassical economic theory.

Specific factors determine whether a good is elastic or inelastic. For demand, the availability of substitutes is a major factor. If many substitutes exist, a consumer can easily switch to a cheaper option, making demand elastic. If a good is a necessity, such as petrol, demand is often inelastic. Addictive goods, like cigarettes, also tend to be inelastic. Other inelastic goods include items that are bought infrequently or represent a small part of a person's budget, like salt. For supply, elasticity can change depending on the starting price. A supplier might be elastic at low prices but become inelastic at much higher prices.

Elasticity is also used to understand how businesses maximize their revenue. A firm can use elasticity to decide whether to raise or lower prices. If demand is inelastic, a firm can increase prices to raise total revenue. If demand is elastic, the firm should decrease prices to increase revenue. This is because, in an elastic market, a price drop leads to a large enough increase in quantity to boost total spending. There is a specific point called unit elasticity where revenue is maximized. At this point, a price change is exactly cancelled out by the change in quantity.

Beyond simple buying, elasticity connects to many complex economic systems. It is a vital tool for understanding the incidence of indirect taxation. It also helps explain the distribution of wealth and the theory of the firm. Economists use it to study welfare distribution, including consumer, producer, and government surplus. In microeconomics, elasticity is closely linked to the slope of demand and supply curves. A steeper curve indicates lower price elasticity, while a flatter curve indicates higher elasticity. This allows researchers to use calculus to measure sensitivity in complex markets.