Weekly Assignment 3 Microeconomics Study Guide: Price Elasticity of Demand and Related Concepts

Price Elasticity of Demand

Definition and Measurement

The price elasticity of demand measures how much the quantity demanded of a good responds to changes in its price. It is a key concept in microeconomics for understanding consumer behavior and market dynamics.

• Elasticity quantifies the responsiveness of buyers and sellers to changes in market conditions.

• Calculated as the percentage change in quantity demanded divided by the percentage change in price.

Formula:

$\text{Price Elasticity of Demand} = \frac{\%\ \text{Change in Quantity Demanded}}{\%\ \text{Change in Price}}$

• If elasticity > 1: Demand is elastic (quantity demanded changes more than price).

• If elasticity < 1: Demand is inelastic (quantity demanded changes less than price).

• If elasticity = 1: Demand is unit elastic (quantity demanded changes exactly as price changes).

Determinants of Elasticity

Several factors influence whether demand for a good is elastic or inelastic:

• Availability of substitutes: More substitutes make demand more elastic.

• Necessity vs. luxury: Necessities tend to have inelastic demand; luxuries are more elastic.

• Definition of the market: Narrowly defined markets are more elastic.

• Time horizon: Demand is more elastic over longer periods.

Types of Elasticity

• Perfectly elastic: Any price change leads to infinite change in quantity demanded. Demand curve is horizontal.

• Perfectly inelastic: Quantity demanded does not change as price changes. Demand curve is vertical.

• Unit elastic: Percentage change in quantity equals percentage change in price.

Examples and Applications

• If the price of a good rises from $50 to $53 and quantity demanded falls from 400 to 300, use the midpoint method to calculate elasticity:

$\text{Elasticity} = \frac{(Q_2 - Q_1) / ((Q_2 + Q_1)/2)}{(P_2 - P_1) / ((P_2 + P_1)/2)}$

• Elasticity affects total revenue: If demand is elastic, a price increase decreases total revenue; if inelastic, a price increase increases total revenue.

Income Elasticity of Demand

Definition

Income elasticity of demand measures how the quantity demanded of a good responds to changes in consumer income.

Formula:

$\text{Income Elasticity of Demand} = \frac{\%\ \text{Change in Quantity Demanded}}{\%\ \text{Change in Income}}$

• Positive income elasticity: Good is a normal good (demand increases as income rises).

• Negative income elasticity: Good is an inferior good (demand decreases as income rises).

Elasticity and Total Revenue

Relationship

Total revenue is the product of price and quantity sold. Elasticity determines how changes in price affect total revenue.

• Elastic demand: Price increase leads to lower total revenue.

• Inelastic demand: Price increase leads to higher total revenue.

• Unit elastic: Total revenue remains unchanged when price changes.

Elasticity in Market Analysis

Supply and Demand Elasticity

Elasticity applies to both demand and supply. The responsiveness of supply to price changes can also be measured.

• Elastic supply: Quantity supplied changes significantly with price changes.

• Inelastic supply: Quantity supplied changes little with price changes.

Market Examples

• Oil market: In the short run, demand and supply are often inelastic.

• Drug legalization: Legalizing marijuana increases supply; elasticity affects market outcomes.

Short Answer Applications

Calculating Elasticity Using the Midpoint Method

Given sales data before and after a discount, use the midpoint method to calculate price elasticity for different consumer groups.

• Group I: Sales before discount = 5000, after = 5400

• Group II: Sales before discount = 4500, after = 5500

Apply the midpoint formula for each group to determine which is more responsive to price changes.

Income Elasticity Example

If a consumer's income rises and demand for concert tickets increases while demand for bus rides decreases, calculate the income elasticity for each good.

• Concert tickets: Likely a normal good (positive income elasticity).

• Bus rides: Likely an inferior good (negative income elasticity).

Summary Table: Elasticity Types and Demand Curve Shapes

Elasticity Type	Elasticity Value	Demand Curve Shape	Example
Perfectly Elastic	Infinity	Horizontal	Identical products in competitive markets
Perfectly Inelastic	0	Vertical	Life-saving medicine
Elastic	> 1	Relatively flat	Luxury goods
Inelastic	< 1	Relatively steep	Necessities
Unit Elastic	1	Intermediate slope	Proportional response

Key Terms

• Elasticity: Responsiveness of quantity demanded or supplied to changes in price or income.

• Midpoint method: A formula for calculating percentage changes using the average of initial and final values.

• Total revenue: The total amount received by sellers, calculated as price times quantity sold.

• Normal good: A good for which demand increases as income increases.

• Inferior good: A good for which demand decreases as income increases.

Additional info: Some context and examples have been inferred to clarify the application of elasticity concepts and formulas, as well as the relationship between elasticity and total revenue.