Price elasticity of demand (PED)

Price elasticity of demand, or PED, measures how much the quantity demanded of a product changes when its price changes. Think of it as a measure of 'responsiveness'. If a small price change causes a big change in demand, we say demand is 'price elastic' – like a stretchy elastic band. If a big price change causes only a small change in demand, we say demand is 'price inelastic' – like a stiff, unstretchable rope. Understanding PED is crucial for firms when setting prices and for governments when deciding on taxes.

To get a precise measure of elasticity, we use a formula. The PED for a product is calculated by dividing the percentage change in quantity demanded by the percentage change in price. The result is a number that tells us the type of elasticity. A value greater than 1 means demand is elastic. A value less than 1 means demand is inelastic. A value equal to 1 means demand is unit elastic. Note: Because price and quantity demanded move in opposite directions, the PED value is technically always negative. However, economists usually ignore the minus sign and use the absolute value.

For a business, the most important application of PED is its link to total revenue (Total Revenue = Price × Quantity). The correct pricing strategy depends entirely on the PED of the product. If demand is price elastic (>1), a price cut will lead to a proportionally larger increase in quantity sold, thus increasing total revenue. If demand is price inelastic (<1), a price increase will lead to a proportionally smaller decrease in quantity sold, also increasing total revenue. Getting this relationship wrong can be a costly mistake for a firm.

The PED of a product is not random; it is determined by several factors. The most important are: 1. Availability of Substitutes: The more substitutes a product has, the more elastic its demand. If the price of one brand of coffee rises, people can easily switch to another. 2. Necessity vs. Luxury: Necessities, like bread or electricity, tend to have inelastic demand because people need them regardless of price. Luxuries, like sports cars or designer watches, have elastic demand. 3. Proportion of Income: Products that take up a tiny proportion of a person's income, like a box of matches, have inelastic demand. Products that are a major expense, like a car or a holiday, have elastic demand. 4. Time Period: In the long run, demand becomes more elastic as consumers have more time to find alternatives or change their habits.

PED values exist on a spectrum, which can be visualized with different demand curves. There are five key categories: 1. Perfectly Inelastic (PED = 0): Quantity demanded does not change at all when price changes. The demand curve is a vertical line. 2. Inelastic (0 < PED < 1): Quantity demanded changes by a smaller percentage than price. The demand curve is steep. 3. Unit Elastic (PED = 1): Quantity demanded changes by the exact same percentage as price. 4. Elastic (PED > 1): Quantity demanded changes by a larger percentage than price. The demand curve is relatively flat. 5. Perfectly Elastic (PED = ∞): Any increase in price causes quantity demanded to fall to zero. The demand curve is a horizontal line. This occurs in highly competitive markets where all firms sell an identical product.