The Market System

Main Economic Agents

The market system in macroeconomics is built upon the interactions between two primary groups of economic agents: households and firms. These agents participate in different markets and play distinct roles in the economy.

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

• Firms: Organizations that use factors of production to supply goods and services to product markets. Households purchase these products from firms.

Circular-Flow Diagram

The circular-flow diagram is a simplified model that illustrates the flow of resources, goods, services, and money between households and firms. It omits complexities such as government, financial systems, and foreign trade for clarity.

• Households provide factors of production to firms via factor markets.

• Firms provide goods and services to households via product markets.

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

• Households pay firms for goods and services.

Additional info: The circular-flow diagram is foundational for understanding how money and resources circulate in a closed economy.

Modeling Markets

Perfectly Competitive Market

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

• Many buyers and sellers

• All firms sell identical products

• No barriers to entry for new firms

• Market prices and quantities adjust to clear the market (no persistent shortages or surpluses)

Additional info: Perfect competition is an idealized market structure; real-world markets may deviate from these assumptions.

Demand

Law of Demand

The law of demand describes the inverse relationship between the price of a good and the quantity demanded by consumers.

• As price (P) increases, quantity demanded (QD) decreases.

• As price decreases, quantity demanded increases.

Equation:

Example: Ryan's demand schedule for salmon shows how the quantity of salmon demanded changes as the price per pound varies.

Demand Curve

The demand curve is a graphical representation of the relationship between price and quantity demanded. It typically slopes downward from left to right, reflecting the law of demand.

• Each point on the curve corresponds to a price-quantity pair from the demand schedule.

• Movement along the curve is caused by changes in the price of the good.

Additional info: The slope of the demand curve is explained by the income effect and substitution effect.

Income Effect and Substitution Effect

Two key concepts explain why the demand curve slopes downward:

• Income Effect: When the price of a normal good falls, consumers' real income increases, allowing them to buy more. For inferior goods, a price decrease may lead to less consumption.

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

Example: If salmon becomes cheaper than bagels, consumers may buy more salmon and fewer bagels.

Market Demand

Market demand is the horizontal sum of all individual quantities demanded by consumers at each price level.

• Aggregate demand reflects the total quantity demanded in the market for a given price.

Changes in Quantity Demanded vs. Changes in Demand

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

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

Factors That Influence Demand

• Income: Higher income increases demand for normal goods, decreases demand for inferior goods.

• Prices of Related Goods: Higher price of substitutes increases demand; higher price of complements decreases demand.

• Tastes and Preferences

• Demographics: Number of buyers in the market.

• Expectations: Future price and income expectations.

Example: If the price of peanut butter rises, demand for jelly (a complement) may decrease.

Supply

Law of Supply

The law of supply states that there is a direct relationship between the price of a good and the quantity supplied by producers.

• As price (P) increases, quantity supplied (QS) increases.

• As price decreases, quantity supplied decreases.

Equation:

Example: Pure Food Fish's supply schedule for salmon shows how quantity supplied changes with price.

Market Supply

Market supply is the horizontal sum of all individual quantities supplied by sellers at each price level.

Changes in Quantity Supplied vs. Changes in Supply

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

• Change in Supply: Caused by changes in non-price factors (input costs, technology, prices of related goods, number of firms, expectations, taxes/subsidies); represented by a shift of the entire supply curve.

Factors That Influence Supply

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

• Technology: Advances increase supply.

• Prices of Related Goods in Production: Higher price of substitutes increases supply; higher price of complements decreases supply.

• Number of Firms: More firms increase market supply.

• Expectations: Future price expectations 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.

• At prices below equilibrium, there is excess demand (shortage).

• At prices above equilibrium, there is excess supply (surplus).

Example: If the equilibrium price for milk is $3.50 per gallon and the equilibrium quantity is 4,000 gallons, the market clears at this point.

Effects of Shifts in Demand and Supply

Shifts in demand or supply curves affect equilibrium price and quantity:

• Increase in Demand: Raises equilibrium price and quantity.

• Decrease in Demand: Lowers equilibrium price and quantity.

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

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

• Simultaneous shifts can reinforce or offset each other's effects on price and quantity.

Additional info: Graphical analysis is often used to illustrate these shifts and their effects.

Quantitative Demand and Supply Analysis

Market equilibrium can be calculated using demand and supply equations.

• Example: For apartments in Baltimore:

(if )

• Set to solve for equilibrium price and quantity.

Additional info: Price controls, such as rent ceilings, can prevent the market from reaching equilibrium, resulting in shortages or surpluses.

Conclusion

The supply and demand model is a powerful tool for explaining market changes and predicting the effects of various economic events. In competitive markets, prices adjust to eliminate surpluses and shortages, moving the market toward equilibrium.