Microeconomics Study Guide: Elasticity, Market Structures, and Labour Demand

Chapter 4: Elasticity

Introduction to Elasticity

Elasticity measures how much buyers and sellers respond to changes in market conditions. It provides a more detailed understanding of supply and demand by quantifying responsiveness to changes in price, income, and the prices of related goods.

• Elasticity: A measure of how much quantity demanded or supplied responds to changes in determinants such as price, income, or related goods.

• Formula: $E = \frac{\%\ \text{Change in Q}}{\%\ \text{Change in Determinant}}$

• Determinants: Price, income, and prices of related goods.

Types of Elasticity

• Own-Price Elasticity of Demand (Ep): Measures how much the quantity demanded of a good responds to a change in its own price.

• Income Elasticity: Measures how quantity demanded changes as consumer income changes.

• Cross-Price Elasticity: Measures how quantity demanded of one good responds to a change in the price of another good.

Types of Demand Elasticity

1. Inelastic Demand: Quantity demanded does not respond strongly to price changes. $|E_p| < 1$ Example: Necessities like water and electricity.

2. Elastic Demand: Quantity demanded responds strongly to price changes. $|E_p| > 1$ Example: Luxury goods, most manufactured goods.

3. Perfectly Inelastic Demand: Quantity demanded does not respond at all to price changes. $E_p = 0$ Example: Prescription heart medication.

4. Perfectly Elastic Demand: Quantity demanded changes infinitely with any change in price. $E_p = \infty$ Example: Goods in perfectly competitive markets.

5. Unit Elastic: Quantity demanded changes by the same percentage as the price. $|E_p| = 1$

Calculating Price Elasticity of Demand

• Formula: $E_p = \frac{\%\ \text{Change in Qd}}{\%\ \text{Change in P}}$

• Example: If the price of milk increases by 2% and Qd decreases by 0.5%, $E_p = -0.25$ (inelastic demand).

• Point Elasticity: $E_p = \frac{dQ}{dP} \times \frac{P}{Q}$

• Always report elasticity as a positive value (absolute value), even though the law of demand makes it negative.

Determinants of Elasticity

• Availability of Substitutes: More substitutes = more elastic demand.

• Necessity vs. Luxury: Necessities are inelastic; luxuries are elastic.

• Definition of Market: Narrowly defined markets are more elastic.

• Time Horizon: Demand is more elastic in the long run.

Chapter 6: Price Controls

Price Ceilings

Price ceilings are legal maximums on the price at which a good can be sold. They are usually enacted when policymakers believe the market price is unfair to buyers.

• Binding Price Ceiling: Set below equilibrium price, causing shortages.

• Non-binding Price Ceiling: Set above equilibrium price, has no effect.

• Example: Rent control in housing markets.

Effects of Price Ceilings

• Shortages (quantity demanded exceeds quantity supplied).

• Non-price rationing (waiting lists, discrimination, bribes).

• Black markets may develop.

• Long-run shortages are larger than short-run shortages.

Numerical Example

Given demand and supply equations for apartments, equilibrium price and quantity can be found by setting Qd = Qs. Imposing a price ceiling below equilibrium creates a shortage.

Chapter 8: Perfect Competition and Revenue

Perfect Competition

A perfectly competitive market has many buyers and sellers, homogeneous products, and no barriers to entry or exit. Firms are price takers and cannot influence the market price.

• Goods are identical (homogeneous).

• Firms can freely enter and exit the market.

• No single firm can influence the market price.

Total, Average, and Marginal Revenue

• Total Revenue (TR): $TR = P \times Q$

• Average Revenue (AR): $AR = \frac{TR}{Q}$

• Marginal Revenue (MR): $MR = \frac{\Delta TR}{\Delta Q}$

• For perfectly competitive firms: $MR = P$

Profit Maximization

• Firms maximize profit where $MR = MC$.

• For perfect competition: $P = MR = MC$

• Profit: $\pi = TR - TC$

• Profit per unit: $\pi = (P - ATC)Q$

Short-Run Profit and Loss

• If $P > ATC$, firm makes positive economic profit.

• If $P < ATC$, firm makes a loss.

• If $P = ATC$, firm makes zero economic profit (normal profit).

Short-Run Shutdown Decision

• Firm should shut down if $P < AVC$ (cannot cover variable costs).

• Shutdown is temporary; exit is permanent.

• Firm's short-run supply curve is the portion of MC above minimum AVC.

Long-Run Entry and Exit

• Firms enter if $P > min ATC$ (positive economic profit).

• Firms exit if $P < min ATC$ (losses).

• In long-run equilibrium, $P = min ATC$ and firms earn zero economic profit.

Efficient Scale

• Efficient scale is the quantity that minimizes average total cost (ATC).

Chapter 10: Monopolistic Competition

Characteristics of Monopolistic Competition

• Many sellers.

• Product differentiation (each firm's product is slightly different).

• Free entry and exit.

• Firms have some control over price due to differentiation.

• Examples: Restaurants, most retailers.

Profit Maximization in Monopolistic Competition

• Firms maximize profit where $MR = MC$.

• Price is set from the demand curve at the profit-maximizing quantity.

• In the short run, firms can make profits or losses.

• In the long run, entry and exit drive profits to zero.

Entry and Exit by Firms

• Short-run profits attract new firms, shifting demand left for existing firms.

• Short-run losses cause firms to exit, shifting demand right for remaining firms.

• Long-run equilibrium: $P = ATC$, zero economic profit.

Comparison: Monopolistic vs. Perfect Competition

• Monopolistic competition: $MC < P = ATC$ at equilibrium, not at minimum ATC.

• Perfect competition: $P = min ATC$ at equilibrium (efficient scale).

• Monopolistic competition results in excess capacity (producing less than efficient scale).

Advertising and Deadweight Loss

• Firms advertise to differentiate products and attract customers.

• Advertising can provide information but may also manipulate tastes and reduce competition.

• Monopolistic competition creates deadweight loss (DWL) due to inefficiency, similar to monopoly.

• DWL Calculation: $\text{DWL} = \frac{1}{2} \times \text{base} \times \text{height}$ (area between MC and demand at Qmonopolistic and Qefficient).

Chapter 12: Labour Demand

Factors of Production

• Land

• Labour

• Capital (physical assets like buildings, machinery, etc.)

The Labour Market

The labour market is governed by the forces of supply and demand and is typically assumed to be perfectly competitive.

• Firms demand labour to produce goods and services.

• Workers supply labour in exchange for wages.

Labour Demand and Supply

• Labour demand depends on the marginal productivity of labour and the price of output.

• Labour supply is influenced by wage rates, working conditions, and alternative opportunities.

Labour Market Equilibrium

• Equilibrium wage and employment are determined where labour demand equals labour supply.

• Shifts in demand or supply can change equilibrium outcomes.

Summary Table: Types of Demand Elasticity

Type	Elasticity Value	Demand Curve	Example
Perfectly Inelastic	0	Vertical	Prescription medication
Inelastic	< 1	Steep	Water, electricity
Unit Elastic	1	Intermediate	Some manufactured goods
Elastic	> 1	Flat	Luxury goods
Perfectly Elastic	∞	Horizontal	Goods in perfect competition

Additional info: Some explanations and examples have been expanded for clarity and completeness, and formulas have been provided in standard LaTeX format for academic rigor.