The Market System

Introduction to Economic Agents

The market system is a fundamental concept in macroeconomics, describing how resources and goods are allocated through the interactions of different economic agents. The two primary groups in a modern economy are households and firms.

• Households: Individuals or groups who sell factors of production (labor, capital, natural resources, entrepreneurship) to firms in factor markets. In return, they receive payments such as wages, rent, interest, and profit.

• Firms: Organizations that purchase factors of production from households and use them to produce goods and services, which they supply to product markets. Households then buy these products from firms.

The Circular-Flow Diagram

The circular-flow diagram is a simplified model that illustrates the flow of resources, goods, services, and money in an economy. It demonstrates how households and firms interact in two types of markets: factor markets and product markets.

• Households provide factors of production to firms.

• Firms provide goods and services to households.

• Firms pay money to households for the use of factors of production.

• Households pay money to firms for goods and services.

Additional info: The basic circular-flow diagram omits the roles of government, the financial system, and foreign buyers/sellers, focusing on the core relationship between households and firms.

Modeling Markets

Perfectly Competitive Markets

To analyze how markets function, economists often use the model of a perfectly competitive market. This model assumes:

• Many buyers and sellers participate.

• All firms sell identical (homogeneous) products.

• There are no barriers to entry or exit for new firms.

• Market prices and quantities adjust freely in response to market forces, ensuring the market clears (no persistent shortages or surpluses).

Demand

The Law of Demand

The law of demand states that, all else equal, as the price of a good increases, the quantity demanded decreases, and vice versa. This relationship is fundamental to understanding consumer behavior in markets.

• Demand Schedule: A table showing the quantity of a good a consumer will buy at various prices.

• Demand Curve: A graph plotting the relationship between price and quantity demanded, typically downward sloping from left to right.

Example: Ryan’s Demand Schedule for Salmon

Graphical Representation: The demand curve for salmon is downward sloping, reflecting the inverse relationship between price and quantity demanded.

Why is the Demand Curve Downward Sloping?

• Income Effect: When the price of a normal good falls, consumers can buy more with their income, increasing quantity demanded. For inferior goods, a price decrease may lead to less consumption if consumers switch to higher-quality alternatives.

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

Additional info: The opportunity cost of consuming a good changes as its price changes, influencing consumer choices.

Market Demand

Market demand is the horizontal sum of all individual demand curves in the market. At each price, the quantities demanded by all consumers are added together.

Changes in Quantity Demanded vs. Changes in Demand

• Change in Quantity Demanded: Caused by a change in the price of the good itself; represented as a movement along the demand curve.

• Change in Demand: Caused by changes in non-price factors (e.g., income, tastes, prices of related goods); represented as a shift of the entire demand curve.

Factors That Influence Demand

• Income: For normal goods, higher income increases demand; for inferior goods, higher income decreases demand.

• Prices of Related Goods: An increase in the price of a substitute increases demand; an increase in the price of a complement decreases demand.

• Population and Demographics: More buyers increase demand.

• Expectations: Expectations about future prices or income can affect current demand.

Types of Related Goods

• Substitutes: Goods that can replace each other (e.g., butter and margarine).

• Complements: Goods that are consumed together (e.g., peanut butter and jelly).

Supply

The Law of Supply

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

• Supply Schedule: A table showing the quantity of a good a producer will supply at various prices.

• Supply Curve: A graph plotting the relationship between price and quantity supplied, typically upward sloping from left to right.

Example: Pure Food Fish’s Supply Schedule for Salmon

Market Supply

Market supply is the horizontal sum of all individual supply curves in the market. At each price, the quantities supplied by all producers are added together.

Changes in Quantity Supplied vs. Changes in Supply

• Change in Quantity Supplied: Caused by a change in the price of the good itself; represented as a movement along the supply curve.

• Change in Supply: Caused by changes in non-price factors (e.g., input costs, technology); represented as a shift of the entire supply curve.

Factors That Influence Supply

• Cost of Inputs: Higher input costs decrease supply; lower input costs increase supply.

• Technological Change: Improvements in technology increase supply.

• Prices of Related Goods in Production: If the price of a substitute in production rises, supply of the original good may decrease.

• Number of Firms: More firms increase market supply.

• Expectations: Expectations about future prices can affect current supply.

• Taxes and Subsidies: Taxes decrease supply; subsidies increase supply.

Market Equilibrium

Equilibrium Price and Quantity

Market equilibrium occurs where the quantity demanded equals the quantity supplied. The corresponding price is the equilibrium price, and the quantity is the equilibrium quantity.

• Surplus (Excess Supply): Occurs when quantity supplied exceeds quantity demanded at a given price, leading to downward pressure on price.

• Shortage (Excess Demand): Occurs when quantity demanded exceeds quantity supplied at a given price, leading to upward pressure on price.

Effects of Shifts in Demand and Supply

Changes in demand or supply shift the respective curves, affecting equilibrium price and quantity.

• Increase in Demand: Raises both equilibrium price and quantity.

• Decrease in Demand: Lowers both equilibrium price and quantity.

• Increase in Supply: Lowers equilibrium price but raises equilibrium quantity.

• Decrease in Supply: Raises equilibrium price but lowers equilibrium quantity.

• Simultaneous Shifts: The effect on price or quantity depends on the relative magnitude and direction of the shifts.

Summary Table: Effects of Demand and Supply Shifts on Equilibrium

Additional info: The question marks indicate that the direction of change depends on the relative size of the shifts in demand and supply.

Quantitative Demand and Supply Analysis

Solving for Market Equilibrium

To find the equilibrium price and quantity, set the demand and supply equations equal to each other and solve for the unknowns.

• Example: Suppose the market for apartments in Baltimore is described by:

Demand: Supply: , for

• Set to solve for equilibrium price and quantity .

Additional info: If a price ceiling (e.g., $P_C = $1,300) is imposed below equilibrium, the quantity supplied will be less than quantity demanded, resulting in a shortage.

Conclusion

The supply and demand model is a powerful tool for understanding how competitive markets function. It explains how prices adjust to eliminate shortages and surpluses, ensuring that markets move toward equilibrium.