Elasticity of Demand and Supply: Measuring Responsiveness

Elasticity of Demand and Supply

Elasticity measures how sensitive buyers and sellers are to changes in price or other factors. It helps economists understand market behavior, predict price changes, and design effective policies.

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1. Introduction to Elasticity

Elasticity is a measure of how much one economic variable responds to a change in another variable. It is expressed as a percentage change and is unitless.

Why is Elasticity Important?

• Helps businesses set prices.
• Helps governments design taxes and subsidies.
• Explains why some goods are more sensitive to price changes than others.

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2. Price Elasticity of Demand (PED)

Price Elasticity of Demand (PED) measures how much the quantity demanded of a good changes when its price changes.

Formula for PED

$$PED=\frac{\%\text{ Change in Quantity Demanded}}{\%\text{ Change in Price}}$$

Types of PED

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3. Factors Affecting PED

Several factors influence how elastic or inelastic demand is:

Factors Influencing PED

• Availability of Substitutes: More substitutes → More elastic demand.
• Necessity vs. Luxury: Necessities (e.g., medicine) have inelastic demand.
• Proportion of Income: If a good costs a large portion of income, demand is more elastic.
• Time Period: Demand becomes more elastic over time.

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4. Total Expenditure (Revenue) and PED

Total expenditure (or revenue) depends on price and quantity demanded.

How PED Affects Total Expenditure

• If PED > 1 (Elastic): A price decrease increases total expenditure.
• If PED < 1 (Inelastic): A price decrease decreases total expenditure.
• If PED = 1 (Unit Elastic): Total expenditure remains unchanged.

Example: Total Expenditure and PED

Suppose a store sells 100 units of a good at ₹100 each.

• Initial Total Expenditure: ₹100 × 100 = ₹10,000
• Price increases to ₹120, quantity demanded drops to 80 units (PED = 0.5, inelastic):
  • New Total Expenditure: ₹120 × 80 = ₹9,600 (decreases)
• Price decreases to ₹80, quantity demanded rises to 120 units (PED = 1.5, elastic):
  • New Total Expenditure: ₹80 × 120 = ₹9,600 (increases)

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5. Price Elasticity of Supply (PES)

Price Elasticity of Supply (PES) measures how much the quantity supplied of a good changes when its price changes.

Formula for PES

$$PES=\frac{\%\text{ Change in Quantity Supplied}}{\%\text{ Change in Price}}$$

Types of PES

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6. Factors Affecting PES

Several factors influence how elastic or inelastic supply is:

Factors Influencing PES

• Production Time: Longer production time → More elastic supply.
• Storage Possibility: Goods that can be stored have more elastic supply.
• Flexibility of Production: Easier to adjust production → More elastic supply.
• Cost of Production: If production costs rise sharply, supply becomes inelastic.

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7. Cross Elasticity of Demand (XED)

Cross Elasticity of Demand (XED) measures how much the demand for one good changes when the price of another good changes.

Formula for XED

$$XED=\frac{\%\text{ Change in Quantity Demanded of Good A}}{\%\text{ Change in Price of Good B}}$$

Types of XED

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8. Income Elasticity of Demand (YED)

Income Elasticity of Demand (YED) measures how much the demand for a good changes when income changes.

Formula for YED

$$YED=\frac{\%\text{ Change in Quantity Demanded}}{\%\text{ Change in Income}}$$

Types of YED

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9. Comparison of Elasticities

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10. Applications of Elasticity

Elasticity has many real-world applications:

Applications of Elasticity

• Businesses: Set optimal prices to maximize revenue.
• Governments: Design taxes and subsidies (e.g., taxing inelastic goods like cigarettes).
• Consumers: Make better purchasing decisions.
• Economists: Predict market trends and policy impacts.

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11. Solved Example: Calculating PED

Question: If the price of a good increases from ₹50 to ₹70, and quantity demanded decreases from 100 units to 80 units, calculate the PED.

Solution:

1. Calculate % change in price: $$\frac{70-50}{50}\times 100=40\%$$

2. Calculate % change in quantity demanded: $$\frac{80-100}{100}\times 100=-20\%$$

3. Calculate PED: $$PED=\frac{-20\%}{40\%}=-0.5$$

Interpretation: The PED is 0.5 (inelastic), meaning demand is not very responsive to price changes.

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12. Solved Example: Calculating PES

Question: If the price of a good increases from ₹100 to ₹120, and quantity supplied increases from 50 units to 70 units, calculate the PES.

Solution:

1. Calculate % change in price: $$\frac{120-100}{100}\times 100=20\%$$

2. Calculate % change in quantity supplied: $$\frac{70-50}{50}\times 100=40\%$$

3. Calculate PES: $$PES=\frac{40\%}{20\%}=2$$

Interpretation: The PES is 2 (elastic), meaning supply is very responsive to price changes.

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13. NEB Board-Style Questions

Short Answer Questions

1. Define Price Elasticity of Demand. What are the factors affecting PED?
2. Explain the difference between elastic and inelastic demand with examples.
3. How does total expenditure change when price changes in elastic and inelastic demand?
4. What is Cross Elasticity of Demand? Give an example of substitutes and complements.
5. Why is the supply of land perfectly inelastic?

Long Answer Questions

6. Explain the concept of Price Elasticity of Supply. Discuss the factors affecting PES with examples.
7. How does elasticity help businesses and governments in decision-making? Explain with examples.
8. Calculate the PED if the price of a good increases by 10% and the quantity demanded decreases by 20%. What does this indicate about the demand?
9. What is Income Elasticity of Demand? How does it help in classifying goods?
10. Explain the relationship between price and total expenditure in elastic and inelastic demand.

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14. Exam Tip

• Understand the formulas: Always remember the formulas for PED, PES, XED, and YED.
• Use real-life examples: Relate concepts to everyday goods (e.g., salt, cars, tea, coffee).
• Compare elastic and inelastic: Know the difference and give examples for each type.
• Practice calculations: NEB often asks for numerical problems on elasticity.
• Focus on applications: Explain how elasticity affects businesses, governments, and consumers.
• Draw graphs: Always draw demand and supply curves to illustrate elastic and inelastic cases.

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Good luck with your NEB exams! Keep practicing and stay focused.