Grade 9 Economics Unit 4: Introduction to Demand and Supply

This unit 4, “Introduction to Demand and Supply,” introduces the foundational forces that drive market economies. You will learn to define demand and supply, understand the laws that govern them, and see how they interact to determine market equilibrium—the price and quantity where buyers and sellers agree.

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Chapter 4.1 – The Concept of Demand

This chapter focuses on the consumer side of the market.

• Definition: Learn what demand means in an economic context—it’s not just wanting something, but having the willingness and ability to buy it.
• Law of Demand: Understand the inverse relationship between price and quantity demanded: as price goes up, quantity demanded usually goes down (ceteris paribus).
• Key Terms: Explore concepts like demand schedule, demand curve, and demand function.

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Chapter 4.2 – The Concept of Supply

This chapter shifts focus to the producer side of the market.

• Definition: Learn what supply represents—the quantity of goods producers are willing and able to sell at various prices.
• Law of Supply: Understand the direct relationship between price and quantity supplied: as price increases, producers are generally willing to supply more.
• Key Terms: Explore the supply schedule, supply curve, and supply function.

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Chapter 4.3 – Market Equilibrium

This section brings demand and supply together to explain how prices are set.

• Equilibrium: Discover how the interaction of buyers (demand) and sellers (supply) determines the equilibrium price and equilibrium quantity.
• Market Dynamics: Learn how the market naturally moves toward this balance point where the quantity demanded equals the quantity supplied .

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Learning Outcomes

By the end of this unit, you will be able to:

• Define the concepts of demand and supply.
• Explain the laws governing demand and supply.
• Describe the equilibrium price and quantity.