Price Elasticity of Demand: Meaning, Types, Formula & Examples

What Is Price Elasticity of Demand?

Price elasticity of demand measures how much the quantity demanded of a product changes when its price changes, while other relevant factors are held constant. It helps students understand why a small price change can cause a large change in demand for some products but only a small change for others.

In economics, elasticity connects a percentage change in quantity demanded with a percentage change in price. It is especially useful for analysing consumer behaviour, pricing decisions and business revenue.

Price Elasticity of Demand Formula

The basic formula is:

Price Elasticity of Demand (Ed) = Percentage change in quantity demanded ÷ Percentage change in price

Because price and quantity demanded generally move in opposite directions, elasticity of demand is often negative when calculated mathematically. In school-level analysis, the absolute value is commonly used to classify elasticity.

### Simple Example Suppose the price of a product increases by 10% and quantity demanded falls by 20%.

Ed = 20% ÷ 10% = 2

The demand is therefore elastic because the percentage change in quantity demanded is greater than the percentage change in price.

Types of Price Elasticity of Demand

### 1. Perfectly Inelastic Demand Quantity demanded remains unchanged even when price changes. The elasticity is zero. This is a theoretical extreme and is represented by a vertical demand curve.

### 2. Relatively Inelastic Demand Quantity demanded changes by a smaller percentage than price. Ed is less than 1. Essential goods often show relatively inelastic demand, although the actual response depends on the market and available substitutes.

### 3. Unitary Elastic Demand The percentage change in quantity demanded equals the percentage change in price. Ed equals 1.

### 4. Relatively Elastic Demand Quantity demanded changes by a larger percentage than price. Ed is greater than 1. Products with close substitutes can often be more price-sensitive.

### 5. Perfectly Elastic Demand A very small price increase causes demand to fall to zero at the market price. It is represented by a horizontal demand curve and is mainly a theoretical case.

Determinants of Price Elasticity

Several factors influence elasticity: availability of substitutes, whether the product is a necessity or luxury, proportion of income spent on the product, time available to adjust consumption, number of uses and consumer habits.

For example, if consumers can quickly switch from one brand to another, demand for an individual brand may be more elastic. If there are few alternatives, demand may be less responsive.

Elasticity and Total Revenue

Elasticity is important for business pricing decisions. When demand is elastic, a price increase can reduce total revenue if the fall in quantity demanded is proportionally larger. When demand is inelastic, a price increase can increase total revenue, subject to the assumptions of the model.

This is why economics students should learn elasticity not only as a formula but also as a tool for interpreting real business decisions.

Elasticity vs Demand

Demand describes the quantity consumers are willing and able to buy at different prices. Elasticity measures the degree of responsiveness of that demand to a change in a determinant such as price.

So, demand and elasticity are related, but they are not the same concept.

Exam-Focused Example

If price falls from ₹100 to ₹90 and quantity demanded rises from 100 units to 120 units, students should first calculate the percentage changes using the method prescribed by their syllabus or question. Then interpret the resulting elasticity rather than stopping at the numerical answer.

Always write the formula, substitute values clearly, calculate carefully and conclude whether demand is elastic, inelastic or unitary.

Quick Revision

1. Elasticity measures responsiveness.
2. Price elasticity compares percentage changes in quantity demanded and price.
3. Ed greater than 1 means relatively elastic demand.
4. Ed less than 1 means relatively inelastic demand.
5. Ed equal to 1 means unitary elasticity.
6. Substitutes, necessity, income share and time affect elasticity.
7. Elasticity can help explain pricing and revenue decisions.

FAQs

### What is price elasticity of demand? It measures the responsiveness of quantity demanded to a change in price.

### Why is elasticity important in economics? It helps explain consumer response and supports analysis of pricing, revenue and market behaviour.

### What is the formula for elasticity of demand? Price elasticity is calculated as percentage change in quantity demanded divided by percentage change in price.

### Is elasticity important for commerce exams? Yes. It is a core microeconomics concept and is useful for definitions, numerical questions, diagrams and case-based answers.

Final Takeaway

Price elasticity of demand becomes easier when you connect the formula with consumer behaviour. Learn the five types, understand the determinants and practise numerical examples so you can explain both the calculation and its economic meaning.