Supply and Demand

Introduction to Supply and Demand

Supply and demand are fundamental concepts in macroeconomics, describing how prices and quantities of goods and services are determined in markets. These concepts help explain consumer and producer behavior, market equilibrium, and the effects of external changes on the economy.

Core Concepts

Scarcity and Choice

• Scarcity: Resources are limited, but human wants are virtually unlimited. This creates the need for choice.

• Consumer Problem: Consumers must decide how to allocate their limited resources to best satisfy their wants.

• Consumer Demand: The amount of a good or service that consumers are willing and able to purchase at various prices, holding other factors constant.

The Law of Demand

Definition and Explanation

• Law of Demand: All else equal, as the price of a good increases, the quantity demanded decreases; as the price decreases, the quantity demanded increases.

• Downward Sloping Demand Curve: The demand curve slopes downward due to two main effects:

  • Substitution Effect: When the price of a good rises, its opportunity cost increases, leading consumers to substitute away from it.

  • Income Effect: A higher price reduces consumers' purchasing power, so they buy less of the good.

Exceptions to the Law of Demand

• Inferior Goods: In rare cases, such as during a famine, demand for certain inferior goods (e.g., potatoes) may increase even as prices rise.

• Veblen Goods: Some goods are bought for their status; higher prices may increase their desirability (e.g., luxury cars).

• Speculative Demand: In finance, rising prices may attract more buyers (e.g., stocks).

Demand Schedule and Demand Curve

Definitions

• Demand Schedule: A table showing the relationship between price and quantity demanded, holding other factors constant.

• Demand Curve: A graphical representation of the demand schedule, typically downward sloping.

Movement Along the Demand Curve

• Change in Price: Movement along the curve occurs when the price changes, holding other factors constant.

• Upward Movement: Higher price, lower quantity demanded.

• Downward Movement: Lower price, higher quantity demanded.

Shifting the Demand Curve

• Change in Demand: Occurs when a non-price factor changes (e.g., income, tastes, prices of related goods).

• Rightward Shift: Increase in demand at every price.

• Leftward Shift: Decrease in demand at every price.

Factors That Shift the Demand Curve

• Prices of Related Goods: Substitutes and complements affect demand.

• Expected Future Prices: Anticipation of price changes can shift demand.

• Income: Higher income increases demand for normal goods, decreases for inferior goods.

• Population: More people, more demand.

The Law of Supply

Definition and Explanation

• Law of Supply: All else equal, as the price of a good increases, the quantity supplied increases; as the price decreases, the quantity supplied decreases.

• Upward Sloping Supply Curve: Suppliers are willing to produce more at higher prices to cover increasing marginal costs.

Supply Schedule and Supply Curve

• Supply Schedule: A table showing the relationship between price and quantity supplied.

• Supply Curve: A graphical representation of the supply schedule, typically upward sloping.

Movement Along the Supply Curve

• Change in Price: Movement along the curve occurs when the price changes, holding other factors constant.

• Upward Movement: Higher price, higher quantity supplied.

• Downward Movement: Lower price, lower quantity supplied.

Shifting the Supply Curve

• Change in Supply: Occurs when a non-price factor changes (e.g., input costs, technology).

• Rightward Shift: Increase in supply at every price.

• Leftward Shift: Decrease in supply at every price.

Factors That Shift the Supply Curve

• Costs of Production: Higher costs decrease supply.

• Prices of Related Goods: Supply may decrease if the price of a substitute in production rises.

• Expected Future Prices: Anticipation of higher prices may reduce current supply.

• Number of Suppliers: More suppliers increase market supply.

• Technological Advances: Lower marginal costs increase supply.

• Disasters: Events like pandemics can sharply decrease supply.

Market Equilibrium

Definition and Determination

• Equilibrium: The point where quantity supplied equals quantity demanded.

• Equilibrium Price: The price at which the market clears.

• Equilibrium Quantity: The quantity bought and sold at the equilibrium price.

• Adjustment: Prices adjust when there is a mismatch between supply and demand.

Disequilibrium: Shortages and Surpluses

• Price Too Low: Quantity demanded exceeds quantity supplied, creating a shortage and upward pressure on prices.

• Price Too High: Quantity supplied exceeds quantity demanded, creating a surplus and downward pressure on prices.

Effects of Changes in Demand and Supply

Change in Demand

• Increase in Demand: Shifts the demand curve rightward, raising both equilibrium price and quantity.

• Decrease in Demand: Shifts the demand curve leftward, lowering both equilibrium price and quantity.

Change in Supply

• Increase in Supply: Shifts the supply curve rightward, lowering equilibrium price and increasing quantity.

• Decrease in Supply: Shifts the supply curve leftward, raising equilibrium price and lowering quantity.

Simultaneous Changes in Supply and Demand

• Both Increase: Equilibrium quantity increases; effect on price is ambiguous.

• Opposite Changes: Increase in demand and decrease in supply raises price; effect on quantity is ambiguous.

Supply and Demand as a Theory of Value

Discussion

• Value Determination: The scarcity and desirability of a good determine its price.

• Examples: Water is essential but cheap due to abundance; caviar is expensive due to scarcity.

Price Controls and Market Outcomes

Types and Effects

• Rent Controls: Intended to make housing affordable, but may lead to shortages and reduced investment.

• Minimum Wage: Evidence on employment effects is mixed; some studies show increases, others show decreases.

• Other Controls: Price controls to fight inflation or fix prices can distort market outcomes.

Key Formulas

Demand and Supply Functions

• General Demand Function:

• General Supply Function:

• Where:

  • = Quantity demanded

  • = Quantity supplied

  • = Price of the good

  • = Income

  • = Price of substitutes

  • = Price of complements

  • = Tastes and preferences

  • = Expectations

  • = Number of buyers/sellers

  • = Costs of production

Summary Table: Factors Shifting Demand and Supply

Example: Market for Fast Food

• If the minimum wage increases, the cost of production for fast food rises, potentially shifting the supply curve leftward.

• Studies (e.g., Card and Krueger) have found mixed effects on employment, with some showing increases in jobs despite higher wages.

Additional info: Academic context and definitions have been expanded for clarity and completeness.