Demand and Supply: Foundations of Microeconomics

Demand and Supply

Competitive Market

A competitive market is characterized by many buyers and sellers of the same good or service, where no single participant can influence the market price. This forms the basis for the analysis of demand and supply in microeconomics.

• Many buyers and sellers: Ensures that individual actions do not affect the overall market price.

• Standardized good or service: All units are considered identical from the perspective of buyers and sellers.

Example Table: Quantity Demanded at Different Prices

Price ($)	Quantity Demanded
10	10
8	20
6	30
4	40
2	50

Law of Demand

The law of demand states that, all else equal, as the price of a product falls, the quantity demanded increases. This relationship is fundamental to consumer behavior in economics.

• Substitution Effect: When the price of a good falls, it becomes relatively cheaper compared to substitutes, leading consumers to buy more of it.

• Income Effect: A lower price increases consumers' purchasing power, allowing them to buy more.

• Inverse Relationship: Quantity demanded is inversely related to price.

Equation:

$Q_d = f(P)$ Where $Q_d$ is quantity demanded and $P$ is price; as $P$ decreases, $Q_d$ increases.

Shifts vs. Movements Along the Demand Curve

It is important to distinguish between a change in quantity demanded (movement along the curve due to price change) and a change in demand (shift of the curve due to other factors).

• Movement along the curve: Caused only by changes in the price of the good itself.

• Shift of the curve: Caused by changes in non-price determinants.

Determinants of Demand (Shifts in Demand Curve)

Several factors can shift the demand curve, changing the quantity demanded at every price.

• Change in income: Affects demand for normal and inferior goods.

• Change in prices of related goods or services: Includes substitutes and complements.

• Change in tastes: Preferences, seasonal changes, or fads.

• Change in number of consumers: Population changes affect market demand.

• Change in expectations: Anticipation of future prices or income.

Normal goods: Demand increases as income increases. Inferior goods: Demand decreases as income increases.

Changes in Price of Related Goods

The demand for a good can be affected by changes in the price of related goods:

• Substitute goods: A decrease in the price of one leads to a decrease in demand for the other.

• Complement goods: A decrease in the price of one leads to an increase in demand for the other.

Supply

Supply refers to the quantity of a good or service that producers are willing and able to sell at various prices over a given period.

• Supply curve: Shows the relationship between price and quantity supplied.

• Quantity supplied: The amount producers are willing to sell at a specific price.

Example Table: Quantity Supplied at Different Prices

Price ($)	Quantity Supplied
2	10
4	20
6	30
8	40
10	50

Law of Supply

The law of supply states that, all else equal, as the price of a good increases, the quantity supplied increases.

• Direct relationship: Quantity supplied rises as price rises.

Equation:

$Q_s = f(P)$ Where $Q_s$ is quantity supplied and $P$ is price; as $P$ increases, $Q_s$ increases.

Movements vs. Shifts in Supply Curve

• Movement along the supply curve: Caused only by changes in the price of the good.

• Shift of the supply curve: Caused by changes in other variables (e.g., input prices, technology, number of sellers).

Summary Table: Differences Between Demand and Supply

Aspect	Demand	Supply
Law	Inverse relationship with price	Direct relationship with price
Curve Shift Causes	Income, tastes, related goods, population, expectations	Input prices, technology, number of sellers, expectations
Movement Along Curve	Price change only	Price change only

Example: If the price of coffee increases, the quantity demanded of coffee decreases (law of demand), while the quantity supplied increases (law of supply).

Additional info: Academic context and definitions have been expanded for clarity and completeness. Tables have been reconstructed and some entries inferred for illustrative purposes.