Chapter 5: Market Equilibrium

Overview

• This chapter builds on consumer and firm behavior from Chapters 2 and 4.
• Focuses on market equilibrium through demand-supply analysis.
• Examines effects of demand and supply shifts on equilibrium.

Key Concepts

• Equilibrium: Situation where market supply equals market demand.
  • Equilibrium Price (p*): Price at which equilibrium is reached.
  • Equilibrium Quantity (q*): Quantity bought and sold at equilibrium price.

Definitions

• Excess Demand: Occurs when market demand exceeds market supply at a given price.
• Excess Supply: Occurs when market supply exceeds market demand at a given price.
• Income Effect: Change in quantity demanded due to change in purchasing power from price change.
• Substitution Effect: Change in quantity demanded when price changes, adjusting for income.

Market Dynamics

• In a perfectly competitive market:
  • Buyers and sellers are price takers.
  • Market equilibrium is achieved when plans of consumers and firms match.

Effects of Shifts in Demand and Supply

• Rightward Shift in Demand: Increases equilibrium quantity; price may increase.
• Leftward Shift in Demand: Decreases equilibrium quantity; price may decrease.
• Rightward Shift in Supply: Increases equilibrium quantity; price may decrease.
• Leftward Shift in Supply: Decreases equilibrium quantity; price may increase.

Simultaneous Shifts

• When both demand and supply curves shift:
  • Effects on equilibrium quantity and price depend on the direction and magnitude of shifts.

Market Equilibrium with Free Entry and Exit

• In markets with free entry and exit, equilibrium price equals minimum average cost.
• No firm earns supernormal profit in equilibrium.

Important Relationships

• Equilibrium Condition: q'(p*) = q°(p*)
• Excess Demand and Supply:
  • Excess Demand (ED): ED(p) = q° - q³
  • Excess Supply (ES): ES(p) = q³ - q°

Conclusion

• Understanding market equilibrium is crucial for analyzing economic behavior and policy implications.

Chapter 5: Market Equilibrium

5.1 Equilibrium, Excess Demand, Excess Supply

• Equilibrium: A situation where the plans of all consumers and firms in the market match, leading to market clearing.
  • *Equilibrium Price (p)**: The price at which market supply equals market demand.
  • *Equilibrium Quantity (q)**: The quantity bought and sold at the equilibrium price.

Key Concepts

• Excess Demand: Occurs when market demand exceeds market supply at a given price.
• Excess Supply: Occurs when market supply exceeds market demand at a given price.

Graphical Representation

• Equilibrium is represented graphically at the intersection of the market demand curve (DD) and market supply curve (SS).

5.1.1 Market Equilibrium: Fixed Number of Firms

• In a perfectly competitive market with a fixed number of firms:
  • Demand Curve (DD): Represents how much consumers are willing to purchase at different prices.
  • Supply Curve (SS): Represents how much firms are willing to supply at different prices.
  • Equilibrium Point: Intersection of DD and SS curves.

Effects of Shifts in Demand and Supply

• If the supply curve shifts rightward (demand unchanged):
  • Equilibrium quantity increases, equilibrium price decreases.
• If both curves shift in the same direction:
  • Effect on equilibrium quantity can be determined; effect on price depends on the magnitude of shifts.
• If curves shift in opposite directions:
  • Price effect can be determined; quantity effect depends on the magnitude of shifts.

5.1.2 Market Equilibrium: Free Entry and Exit

• In a market with free entry and exit:
  • Equilibrium price equals minimum average cost of firms.
  • No firm earns supernormal profit or incurs losses.

Table 5.1: Impact of Simultaneous Shifts on Equilibrium

Important Definitions

• Income Effect: Change in optimal quantity due to change in purchasing power from price change.
• Indifference Curve: Locus of points where the consumer is indifferent among bundles.
• Inferior Good: Demand decreases as consumer income increases.
• Normal Good: Demand increases as consumer income increases.
• Price Ceiling: Government-imposed upper limit on price.
• Price Floor: Government-imposed lower limit on price.

Conclusion

• Understanding market equilibrium is crucial for analyzing how prices and quantities are determined in competitive markets.

Common Mistakes and Exam Tips

Common Pitfalls

• Misunderstanding Equilibrium: Students often confuse equilibrium with a static state. Remember, equilibrium is a dynamic process where supply equals demand.
• Ignoring Shifts in Curves: Failing to account for shifts in demand and supply curves can lead to incorrect conclusions about changes in equilibrium price and quantity.
• Overlooking Market Structures: Not recognizing the implications of different market structures (perfect competition, monopoly, etc.) on equilibrium can lead to errors in analysis.
• Confusing Excess Demand and Excess Supply: Be clear on definitions; excess demand occurs when demand exceeds supply at a given price, while excess supply occurs when supply exceeds demand.

Tips for Exam Preparation

• Understand Key Concepts: Make sure to grasp the definitions of key terms such as equilibrium price, excess demand, and excess supply.
• Practice Graphs: Be comfortable drawing and interpreting supply and demand graphs, including shifts and their effects on equilibrium.
• Review Case Studies: Look at real-world examples of price ceilings and floors to understand their impact on market equilibrium.
• Use Diagrams: When explaining concepts, use diagrams to illustrate shifts in demand and supply and their effects on equilibrium.
• Anticipate Questions: Prepare for questions that ask about the effects of changes in external factors (like income changes or input prices) on equilibrium.