Economics
Elasticity of Demand and Supply Measurement
Quick fact
The elasticity of demand for gasoline is about 0.1, meaning a 10% price increase only reduces quantity demanded by 1%, while the elasticity for fresh tomatoes is around 2.8, so a 10% price rise cuts demand by 28%.
Why this is interesting
Why do rising gas prices almost never force you to buy a different car, but a small sale on headphones can clear the shelves? The answer lies in a surprisingly simple ratio that economists call elasticity.
Read the full explanation
Understanding Elasticity of Demand and Supply Measurement
Think of the demand curve as a rubber band. When you pull on it by raising the price, the quantity demanded stretches. Some goods stretch a lot (elastic), like movie tickets: a slight price rise and people stay home. Others barely stretch (inelastic), like insulin: no matter the price, patients need it. Elasticity is simply the percentage change in quantity divided by the percentage change in price. For example, if the price of coffee rises 10% and you buy 5% less coffee, the price elasticity is -0.5 (we often take the absolute value and say 0.5). Supply works the same way: if a price increase of 10% makes producers offer 20% more wheat, supply elasticity is 2.0. The key is that elasticity is a pure number, free of units, so we can compare apples to oranges, quite literally.
A deeper explanation
The heart of elasticity lies in measuring responsiveness using relative (percentage) changes, which makes it scale-free. The midpoint method (or arc elasticity) avoids ambiguity when moving along the curve by averaging the starting and ending values. Why do we care? Because elasticity determines how total revenue changes when price changes: if demand is elastic (elasticity 1), a price increase reduces total revenue; if inelastic (< 1), a price increase raises revenue. It also reveals why governments face hard choices: when demand is inelastic (like cigarettes), a tax raises a lot of revenue but barely reduces consumption. For supply, elasticity is driven by production flexibility and time; in the short run, factories are fixed, so supply is inelastic, but over time it becomes elastic as firms adjust capacity. These measurements are not just dry numbers: they are vital for setting prices, predicting shocks, and designing public policy.