Elasticity in Microeconomics

Introduction to Elasticity

Elasticity is a fundamental concept in microeconomics that measures how responsive one variable is to changes in another variable. Most commonly, it refers to how the quantity demanded or supplied of a good responds to changes in price, income, or the price of related goods. Understanding elasticity helps explain consumer and producer behavior, and informs policy decisions.

Price Elasticity of Demand

Definition and Interpretation

• Price Elasticity of Demand (PED): The percentage change in quantity demanded resulting from a one percent change in price, holding all else constant.

• Formula:

• Usually negative due to the Law of Demand (as price increases, quantity demanded decreases).

• Elasticity is a unit-free measure, allowing for comparison across goods and markets.

Calculating Percentage Changes

• Change:

• Average Value:

• Percentage Change:

Example: If quantity increases from 100 to 200, , , so .

Elasticity and Slope

• Elasticity is related to the slope of the demand curve, but not identical.

• For a linear demand curve :

• Elasticity varies along a linear demand curve, even though the slope is constant.

Classification of Price Elasticity of Demand

Determinants of Demand Elasticity

• Availability of Substitutes: More substitutes make demand more elastic (e.g., medicine vs. collectibles).

• Proportion of Income: Goods that take a larger share of income tend to have more elastic demand (e.g., cars vs. transit fares).

• Time Horizon: Demand is more elastic in the long run as consumers adjust their behavior.

Examples of Elasticities for Various Goods

Elasticity and Revenue

Total Revenue and Expenditure

• Total Revenue (TR):

• Total Expenditure: (from the buyer's perspective)

• How revenue/expenditure changes with price depends on elasticity.

Effect of Price Changes on Revenue

Other Demand Elasticities

Income Elasticity of Demand

• Definition: The percentage change in quantity demanded per percentage change in income.

• Formula:

• Normal Goods: Positive income elasticity (demand increases as income rises).

• Inferior Goods: Negative income elasticity (demand decreases as income rises).

• Income-Elastic: (luxury goods).

• Income-Inelastic: (necessities).

Cross-Price Elasticity of Demand

• Definition: The percentage change in quantity demanded of good A per percentage change in the price of good B.

• Formula:

• Substitutes: Positive cross-price elasticity.

• Complements: Negative cross-price elasticity.

Price Elasticity of Supply

Definition and Classification

• Price Elasticity of Supply (PES): The percentage change in quantity supplied per percentage change in price.

• Formula:

• Usually positive (Law of Supply).

Determinants of Supply Elasticity

• Availability of Production Substitutes: More substitutes make supply more elastic (e.g., cornfields vs. oil refineries).

• Financial Flexibility: Firms with more resources or insurance can adjust supply more easily.

• Time Horizon: Supply is more elastic in the long run as firms adjust production.

Estimating Elasticities

Empirical Measurement

• Elasticities are estimated using observed data on prices and quantities over time.

• Random or natural experiments (e.g., supply shocks) can help identify demand or supply elasticities.

• Econometric methods are used in advanced courses to estimate elasticities more precisely.

Supply and Demand Shifters

Summary

• Elasticity measures responsiveness of demand or supply to changes in price, income, or related goods' prices.

• Understanding elasticity is crucial for predicting market outcomes and the effects of policy changes.

• Elasticity affects total revenue, expenditure, and the incidence of taxes and subsidies.

Additional info: Some context and examples were inferred and expanded for clarity and completeness, as the original notes were fragmented and included shorthand or incomplete tables.