factors affecting: income elasticity of demand

Price Elasticity of Demand 📈

Price elasticity measures how much the quantity demanded of a good changes when its price changes. Think of it like a rubber band: if the band stretches a lot, the good is elastic; if it barely stretches, the good is inelastic.

Formula & Example

The elasticity coefficient is calculated as:

So,

\$Ed = \frac{\% \Delta Qd}{\% \Delta P}\$

Example: If the price of a smartphone rises from £500 to £550 (a 10% increase) and the quantity sold falls from 1,000 to 900 units (a 10% decrease), then:

\$E_d = \frac{-10\%}{10\%} = -1.0\$

A value of –1.0 indicates unit‑elastic demand – the percentage change in quantity matches the percentage change in price.

Income Elasticity of Demand 💰

Income elasticity tells us how quantity demanded changes when consumers’ incomes change. It helps us classify goods into normal, inferior, or luxury categories.

Key Definitions

• Normal goods: Demand rises when income rises (\$E_y > 0\$).
• Inferior goods: Demand falls when income rises (\$E_y < 0\$).
• Luxury goods: Demand rises more than proportionally with income (\$E_y > 1\$).

Factors Affecting Income Elasticity

• Consumer preferences: Trends can make a good feel more or less luxurious.
• Income distribution: If most people are low‑income, a good may appear inferior until incomes rise.
• Availability of substitutes: More alternatives can lower elasticity.
• Cultural significance: Foods or items tied to culture may have high elasticity during celebrations.
• Economic growth: In a booming economy, people spend more on luxury goods.
• Price changes relative to income: If a good’s price rises faster than income, its effective elasticity may drop.

Illustrative Table

Cross Elasticity of Demand 🔀

Cross elasticity measures how the quantity demanded of one good responds to a price change in another good. It tells us whether goods are substitutes or complements.

Formula & Example

\$E{xy} = \frac{\% \Delta Qx}{\% \Delta P_y}\$

Example: If the price of coffee rises by 5% and the quantity demanded of tea increases by 3%, then:

\$E_{tea,coffee} = \frac{3\%}{5\%} = 0.6\$

A positive value indicates that coffee and tea are substitutes.

Key Takeaways

1. Elasticity helps predict how markets react to price or income changes.
2. Normal goods have positive income elasticity; inferior goods have negative.
3. Luxury goods show high income elasticity (>1).
4. Substitutes have positive cross elasticity; complements have negative.
5. Understanding these concepts is essential for businesses setting prices and for policymakers designing tax or subsidy policies.