What is the difference between price elasticity and income elasticity?

In one line

The rule

Price elasticity measures the change in quantity demanded or supplied when price changes. Income elasticity measures the change in quantity demanded when income changes.

• Price elasticity of demand: Eₚ = (% Change in Quantity Demanded) / (% Change in Price)
• Income elasticity of demand: Eᵧ = (% Change in Quantity Demanded) / (% Change in Income)

Where:

• Eₚ = price elasticity
• Eᵧ = income elasticity
• % Change in Quantity Demanded = (New Q - Old Q) / Old Q × 100
• % Change in Price = (New P - Old P) / Old P × 100
• % Change in Income = (New Income - Old Income) / Old Income × 100

Let's understand it simply

Imagine you love mangoes. If the price of mangoes goes up, you may buy less. This is price elasticity—it shows how much your buying changes when the price changes.

Now, suppose you get a bigger pocket money this month. Will you buy more mangoes? Income elasticity tells us how much your buying changes when your income changes. So, price elasticity is about price, income elasticity is about your income.

How it works

1. Price elasticity:

• The price of a good changes (for example, onions become expensive).
• People buy more or less because of this price change.
• We measure how big this change is compared to the price change.

1. Income elasticity:

• People's income changes (for example, your father gets a bonus).
• People may buy more or less of a good because they have more or less money.
• We measure how much their buying changes compared to the income change.

The story behind it

Economists wanted to know how sensitive people are to changes in price and income. This helps shops, farmers, and the government plan better. The idea of elasticity was first used by Alfred Marshall, a famous British economist, in the late 1800s. He wanted to make economics more like science, using numbers and formulas.

Where you see it in real life

• Vegetable market: If tomato prices double, sellers notice if people stop buying (price elasticity). If people in your area get richer and buy more apples, that's income elasticity.
• Clothes shopping: When Diwali bonuses come, people may buy more new clothes (income elasticity).
• Bus fares: If the city increases bus ticket prices, do fewer people travel by bus? (price elasticity)
• Luxury cars: When incomes rise, more people buy expensive cars (income elasticity is high).
• Salt: Even if salt price rises, most people still buy it (price elasticity is low).
• Mobile phones: If prices drop, more people buy smartphones (price elasticity).

Why it matters

• Helps shopkeepers decide prices: If demand is elastic, a small price rise can lose many customers.
• Helps government set taxes: High taxes on goods with low price elasticity (like petrol) bring more money.
• Helps companies plan: If income elasticity is high, they target richer customers.
• Useful in exams: Many questions ask you to compare or calculate these elasticities.

Common mistakes

• Mixing up the two: Remember, price elasticity is about price changes, income elasticity is about income changes.
• Thinking both always move together: Sometimes, a good can be price inelastic but income elastic (like rice).
• Forgetting the formula: Always check if the question is about price or income before using the formula.

Remember it

Price elasticity = price changes; income elasticity = income changes. P for Price, I for Income.