BackMicroeconomics Chapter 3: Demand, Supply, and Market Equilibrium
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Demand, Supply, and Market Equilibrium
Chapter Overview and Learning Objectives
This chapter introduces the foundational concepts of demand, supply, and the determination of market prices in microeconomics. Students will learn to identify the factors affecting demand and supply, distinguish between movements along and shifts of curves, and analyze market equilibrium.
Demand: Factors determining quantity demanded; shifts vs. movements along the demand curve.
Supply: Factors determining quantity supplied; shifts vs. movements along the supply curve.
Market Price Determination: Forces driving equilibrium price and the effects of changes in demand and supply.
Demand
Quantity Demanded
The quantity demanded of a product is the total amount that consumers desire to purchase during a specific time period. It is distinct from the actual quantity bought, which refers to completed purchases. Quantity demanded is considered a flow variable, measured over a period of time, rather than a stock at a single point.
Definition: The amount consumers wish to buy at a given price over a time period.
Actual purchases: The quantity exchanged in the market.
Flow vs. Stock: Flow is measured per unit time; stock is measured at a point in time.
Quantity Demanded and Price
The basic hypothesis in microeconomics is that, ceteris paribus (all else equal), the price of a product and the quantity demanded are negatively related. This relationship is known as the law of demand.
Law of Demand: As price decreases, quantity demanded increases, and vice versa.
Substitution Effect: Lower prices make a product more attractive compared to alternatives.
Income Effect: Lower prices increase consumers' real income, allowing them to buy more.
Demand Schedules and Demand Curves
A demand schedule lists the quantity demanded at various prices. The demand curve is a graphical representation of this relationship, typically downward sloping.
Reference Point | Price ($ per bushel) | Quantity Demanded (thousands of bushels per year) |
|---|---|---|
U | 20 | 110 |
V | 40 | 85 |
W | 60 | 65 |
X | 80 | 50 |
Y | 100 | 40 |
The demand curve plots price on the vertical axis and quantity demanded on the horizontal axis.
Shifts in the Demand Curve
Changes in variables other than price cause the demand curve to shift. These factors include:
Consumer's income
Prices of other goods
Consumers’ preferences
Population
Significant changes in weather
A rightward shift indicates an increase in demand; a leftward shift indicates a decrease.
Reference Point | Quantity Demanded (Income = $50,000) | Quantity Demanded (Income = $60,000) |
|---|---|---|
U | 110 | 140 |
V | 85 | 115 |
W | 65 | 90 |
X | 50 | 70 |
Y | 40 | 70 |
Example: An increase in consumer income shifts the demand curve for apples to the right, increasing quantity demanded at every price.
Movements Along vs. Shifts of the Demand Curve
Movement along the curve: Caused by a change in the price of the good itself; quantity demanded changes.
Shift of the curve: Caused by changes in other determinants (income, preferences, etc.); demand changes at every price.
Supply
Quantity Supplied
The quantity supplied is the amount of a product that firms are willing to sell during a specific time period. Like quantity demanded, it is a flow variable.
Definition: Amount firms wish to sell at a given price over a time period.
Not necessarily actual sales: May differ from quantity actually sold.
Quantity Supplied and Price
The basic hypothesis is that, ceteris paribus, the price of a product and the quantity supplied are positively related. This is known as the law of supply.
Law of Supply: As price increases, quantity supplied increases, and vice versa.
Profit Motive: Higher prices make production more profitable, encouraging firms to supply more.
Supply Schedules and Supply Curves
A supply schedule lists the quantity supplied at various prices. The supply curve is a graphical representation, typically upward sloping.
Reference Point | Price ($ per bushel) | Quantity Supplied (thousands of bushels per year) |
|---|---|---|
U | 20 | 40 |
V | 40 | 65 |
W | 60 | 85 |
X | 80 | 110 |
Y | 100 | 140 |
Shifts in the Supply Curve
Changes in variables other than price cause the supply curve to shift. These factors include:
Prices of inputs
Technology
Government taxes or subsidies
Prices of other products
Significant changes in weather
Number of suppliers
Example: Improved technology can shift the supply curve for apples to the right, increasing quantity supplied at every price.
Movements Along vs. Shifts of the Supply Curve
Movement along the curve: Caused by a change in the price of the good itself; quantity supplied changes.
Shift of the curve: Caused by changes in other determinants (input prices, technology, etc.); supply changes at every price.
Market Equilibrium
The Concept of a Market
A market is any situation in which buyers and sellers negotiate the transaction of goods or services. Markets vary in the degree of competition. In a perfectly competitive market, all participants are price takers.
Equilibrium Price and Quantity
Market equilibrium occurs where quantity demanded equals quantity supplied. The corresponding price is the equilibrium price, and the quantity is the equilibrium quantity.
At equilibrium: No excess supply or demand; the market "clears".
Above equilibrium price: Excess supply; downward pressure on price.
Below equilibrium price: Excess demand; upward pressure on price.
Equation:
where is quantity demanded and is quantity supplied.
Changes in Market Equilibrium
Increase in demand: Raises both equilibrium price and quantity.
Decrease in demand: Lowers both equilibrium price and quantity.
Increase in supply: Lowers equilibrium price, raises equilibrium quantity.
Decrease in supply: Raises equilibrium price, lowers equilibrium quantity.
Relative Prices and Inflation
The absolute price is the monetary amount required to purchase one unit of a product. The relative price is the price of one good in terms of another. Demand and supply curves are typically drawn in terms of relative prices.
Limitations of the Demand and Supply Model
While the demand and supply model explains many market outcomes, it has limitations and may not apply to all consumer products. For the model to accurately describe price determination, three conditions must be met:
Large number of consumers, each small relative to the market.
Large number of producers, each small relative to the market.
Producers must sell homogeneous versions of the product.
Example: The model works well for apples but not for differentiated products like iPhones.
Application: Demand and Supply Shocks (COVID-19 Pandemic)
During the COVID-19 pandemic, demand for certain goods and services declined, while it increased for others. Supply was also affected by restrictions. Governments responded by increasing spending and borrowing, which involved issuing new bonds.
Demand shock: Sudden change in consumer demand due to external events.
Supply shock: Sudden change in production or availability of goods.
Example: Lockdowns reduced demand for travel but increased demand for home goods.
Additional info: The notes have been expanded with academic context, definitions, and examples to ensure completeness and clarity for exam preparation.
