Chapter 3: Demand, Supply, and Market Equilibrium – Microeconomics Study Notes

Chapter 3: Demand, Supply, and Market Equilibrium

Overview

This chapter introduces the foundational concepts of microeconomics, focusing on how individual markets operate, the role of firms and households, and the mechanisms that determine prices and quantities in market economies.

• Markets: Institutions where exchanges of goods and services take place.

• Key question: How do households and firms answer the three basic economic questions: What to produce? How to produce? For whom to produce?

3.1 Firms and Households: The Basic Decision-Making Units

Firms and households are the primary agents in microeconomic analysis, each playing distinct roles in the economy.

• Firms: Primary producers; transform inputs into outputs and sell products in markets. Their main goal is to maximize profit.

• Households: Primary consumers; supply inputs (labor, capital, land) and demand goods/services.

• Firms exist to produce goods/services people want and are analyzed based on profit maximization.

• Entrepreneurship: Entrepreneurs organize the firm, arrange financing, hire employees, and assume risk. Entrepreneurship is the root of firm creation.

Household Characteristics

• Can consist of any number of people.

• Decisions based on individual tastes and preferences.

• Limited income constrains choices; income is determined by job availability, wages, and accumulated wealth.

3.2 Input and Output Markets: The Circular Flow

The circular flow model illustrates the interactions between households and firms in two main types of markets.

• Product/Output Markets: Firms supply goods/services; households demand them.

• Input/Factor Markets: Households supply inputs (labor, capital, land); firms demand them to produce goods/services.

• Payment flows in the opposite direction of goods/services flows.

Types of Input Markets

• Labor market: Households supply labor, firms pay wages.

• Capital market: Households supply funds, firms use to buy capital goods.

• Land market: Households supply land in exchange for rent.

3.3 Demand in Product/Output Markets

Demand refers to the quantity of a good or service that households are willing and able to purchase at various prices.

Determinants of Household Demand

1. Price of the product

2. Income available

3. Accumulated wealth

4. Prices of other products

5. Tastes and preferences

6. Expectations (e.g., future income)

Quantity Demanded

• The number of units a household would buy if it could purchase all it wanted.

Law of Demand

• As price increases, quantity demanded decreases; as price decreases, quantity demanded increases.

• Inverse relationship, ceteris paribus (all else equal).

• Demand curves slope downward.

Equation:

• $Q_d = a - bP$

Demand Schedule & Demand Curve

• Demand schedule: Table showing quantity demanded at different prices.

• Demand curve: Graphical representation of the demand schedule.

Properties of Demand Curves

• Negative slope (inverse relationship).

• X-intercept (Q): Limited by time and diminishing marginal utility.

• Y-intercept (P): Limited by income/wealth.

• Even at zero price, demand is finite due to time and utility constraints.

Income vs. Wealth

• Income: Flow measure (wages, rent, interest, profit per month/year).

• Wealth: Stock measure (household assets minus debts).

• Net worth: Wealth if household sold everything and repaid debts.

Types of Goods

• Normal goods: Demand increases when income increases (e.g., meals, vacations).

• Inferior goods: Demand decreases when income increases (e.g., bus rides).

Related Goods

• Substitutes: Replace one another (price increase for one increases demand for the other).

• Perfect substitutes: Identical goods.

• Complements: Consumed together (price increase for one decreases demand for the other).

Other Influences

• Future expectations of prices or income can shift demand.

Shifts vs. Movements

• Movement along curve: Caused by a change in the good's own price.

• Shift of curve: Caused by changes in income, preferences, or prices of other goods.

Causes of Increase in Demand (Right Shift)

1. Higher income (normal good)

2. Lower income (inferior good)

3. Decrease in price of a complement

4. Increase in price of a substitute

5. Expectations of higher prices/shortages

6. Positive changes in tastes/preferences

Causes of Decrease in Demand (Left Shift)

1. Lower income (normal good)

2. Higher income (inferior good)

3. Increase in price of a complement

4. Decrease in price of a substitute

5. Expectations of falling prices

6. Negative change in preferences

Market Demand

• Sum of all household demands.

• Market demand curve = sum of individual demand curves.

• Shifts the same way as individual demand curves.

3.4 Supply in Product/Output Markets

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

Basic Concepts

• Firms supply goods to make profit.

• Profit = Revenue – Cost

• Revenue = Price × Quantity sold

Quantity Supplied

• Amount of product firms are willing to sell at a given price per period.

Supply Schedule & Supply Curve

• Supply schedule: Table of quantities supplied at different prices.

• Supply curve: Upward sloping, showing direct relationship between price and quantity supplied.

Law of Supply

• As price increases, quantity supplied increases; as price decreases, quantity supplied decreases.

• Direct relationship, ceteris paribus.

Equation:

• $Q_s = c + dP$

Determinants of Supply

• Price of the good

• Cost of production (input prices, wages, technology)

• Prices of related goods

• Technology (lowers costs, increases supply)

• Input prices: increase → supply decreases; decrease → supply increases

Shifts vs. Movements

• Movement along supply curve: Change in the good's own price.

• Shift of supply curve: Caused by changes in input prices, technology, or related goods.

Causes of Supply Increase (Right Shift)

1. Decrease in input prices

2. Improvement in technology

3. Decrease in price of other goods that could be produced

Causes of Supply Decrease (Left Shift)

1. Increase in input prices

2. Decline in technology (or bad weather)

3. Increase in price of other goods that could be produced

Market Supply

• Sum of all producers' supply at each price.

• Depends on individual firms' supply curves and number of firms.

3.5 Market Equilibrium

Market equilibrium occurs when quantity demanded equals quantity supplied at a particular price, resulting in no tendency for change.

Conditions

• Excess Demand (Shortage): $Q_d > Q_s$ at current price.

• Excess Supply (Surplus): $Q_s > Q_d$ at current price.

• Equilibrium: $Q_d = Q_s$ at current price.

How Equilibrium Works

• Excess demand → price rises until balance.

• Excess supply → price falls until balance.

• At equilibrium, no tendency for change.

• Graphically: equilibrium is intersection of demand and supply curves.

Mathematical Representation

• Inverse demand curve: $P = a - bQ_d$

• Demand curve: $Q_d = a - bP$

• Inverse supply curve: $P = c + dQ_s$

• Supply curve: $Q_s = c + dP$

• Equilibrium: set $Q_d = Q_s$, $a - bP = c + dP$ and solve for $P$.

Shifts and Equilibrium

• Increase in Demand: Equilibrium price increases, quantity increases (right shift).

• Decrease in Demand: Equilibrium price decreases, quantity decreases (left shift).

• Increase in Supply: Equilibrium price decreases, quantity increases (right shift).

• Decrease in Supply: Equilibrium price increases, quantity decreases (left shift).

Summary Table

Concept	Key Points
Demand	Inverse relation with price; shifts based on income, preferences, related goods.
Supply	Direct relation with price; shifts based on input costs, technology, related goods.
Equilibrium	Where $Q_d = Q_s$; market self-adjusts via price changes when shortages/surpluses occur.

Additional info: Mathematical equations and graphical analysis are essential for understanding market equilibrium and the effects of shifts in demand and supply.