Where Prices Come From: The Interac tion of Demand and Supply

Introduction

This chapter explores how prices are determined in phenomena such as price changes and market equilibrium.

The Demand Side of the Market, -

Variables Influencing Demand

Market demand refers to the total demand by all consumers for a given good or service. Several variables influence demand:

• Price of the product

• Income of consumers

• Prices of related goods (substitutes and complements)

• Tastes

• Population and demographics

• Expected future prices

• Natural disasters and pandemics

Demand Schedule and Demand Curve

A demand schedule is a table showing the relationship between price and quantity demanded. The demand curve is a graphical representation of this relationship.

• Quantity demanded: The amount a consumer is willing and able to purchase at a given price.

• Law of demand: Holding all else constant, as the price falls, quantity demanded increases; as price rises, quantity demanded decreases.

Explaining the Law of Demand

• Substitution effect: Consumers substitute toward goods whose price has fallen.

• Income effect: Lower prices increase consumer purchasing power, allowing more purchases.

Ceteris Paribus Condition

When analyzing demand, other variables are held constant (ceteris paribus), isolating the effect of price changes.

Shifting the Demand Curve

Changes in factors other than price cause the entire demand curve to shift:

• A shift to the right indicates an increase in demand.

• A shift to the left indicates a decrease in demand.

Variables That Shift Market Demand

• Income: Demand for normal goods increases with income; demand for inferior goods decreases.

• Prices of related goods: Substitutes and complements affect demand differently.

• Tastes: Changes in consumer preferences can increase or decrease demand.

• Population/Demographics: Larger populations or demographic shifts can increase demand.

• Expected future prices: Anticipation of price changes affects current demand.

• Natural disasters and pandemics: Temporary disruptions can shift demand for certain goods.

Normal and Inferior Goods

• Normal good: Demand increases as income rises (e.g., new clothes, restaurant meals).

• Inferior good: Demand increases as income falls (e.g., second-hand clothes, instant noodles).

Substitutes and Complements

• Substitutes: Goods used for the same purpose (e.g., Big Mac and Whopper).

• Complements: Goods used together (e.g., left and right shoes).

Change in Demand vs. Change in Quantity Demanded

• A change in price causes a movement along the demand curve (change in quantity demanded).

• Any other change causes the demand curve to shift (change in demand).

The Supply Side of the Market

Variables Influencing Supply

Market supply refers to the total amount firms are willing and able to provide at various prices. Key variables include:

• Price of the product

• Prices of inputs

• Technological change

• Prices of related goods in production

• Number of firms in the market

• Expected future prices

• Natural disasters and pandemics

Supply Schedule and Supply Curve

A supply schedule is a table showing the relationship between price and quantity supplied. The supply curve is a graphical representation of this relationship.

• Quantity supplied: The amount a firm is willing and able to supply at a given price.

• Law of supply: Holding all else constant, as price increases, quantity supplied increases; as price decreases, quantity supplied decreases.

Shifting the Supply Curve

• A shift to the right indicates an increase in supply.

• A shift to the left indicates a decrease in supply.

Variables That Shift Market Supply

• Prices of inputs: Higher input prices decrease supply; lower input prices increase supply.

• Technological change: Improvements increase supply; restrictions decrease supply.

• Prices of related goods in production: Substitutes and complements in production affect supply.

• Number of firms: More firms increase supply.

• Expected future prices: Anticipation of higher prices may decrease current supply.

• Natural disasters and pandemics: Disruptions decrease supply.

Change in Supply vs. Change in Quantity Supplied

• A change in price causes a movement along the supply curve (change in quantity supplied).

• Any other change causes the supply curve to shift (change in supply).

Market Equilibrium: Putting Demand and Supply Together

Market Equilibrium

Market equilibrium occurs when quantity demanded equals quantity supplied. In a perfectly competitive market, this is called competitive market equilibrium.

• Equilibrium price: The price at which buyers and sellers agree to trade.

• Equilibrium quantity: The quantity traded at equilibrium price.

Surpluses and Shortages

• Surplus: Quantity supplied exceeds quantity demanded; price tends to fall.

• Shortage: Quantity demanded exceeds quantity supplied; price tends to rise.

The Effect of Demand and Supply Shifts on Equilibrium

Predicting Changes in Price and Quantity

Shifts in demand or supply curves change the equilibrium price and quantity. The direction of change depends on which curve shifts and by how much.

• Increase in demand: Equilibrium price and quantity rise.

• Increase in supply: Equilibrium price falls, equilibrium quantity rises.

Simultaneous Shifts in Demand and Supply

When both curves shift, equilibrium quantity will rise, but the effect on equilibrium price depends on the relative magnitude of the shifts.

Summary Table: Effects of Shifts on Equilibrium

Key Equations

• Demand function:

• Supply function:

• Equilibrium condition:

Conclusion

The demand and supply model is a powerful tool for predicting how changes in market conditions affect prices and quantities. Understanding the distinction between movements along curves and shifts of curves is essential for analyzing real-world economic events.