Introduction: Why Markets Don't Live Alone
Hi there! Welcome to one of the most "connected" parts of Economics. So far, you have looked at how supply and demand work in a single market. But in the real world, markets are like a big web—what happens in one market almost always ripples out to affect others.
In this chapter, we are going to look at intermarket relationships. This is just a fancy way of saying "how markets affect each other." By the end of this page, you’ll understand why a rise in the price of coffee might make tea more popular, or why a sale on printers leads to more ink being sold. Don't worry if this seems a bit like a puzzle at first; we'll piece it together step-by-step!
1. Substitutes: The "Instead Of" Goods
Substitutes are goods that can be used in place of one another. They are rivals! If you can't get one, or if one becomes too expensive, you simply switch to the other because they satisfy the same need.
Common Examples:
- Coke and Pepsi
- Xbox and PlayStation
- Bus travel and Train travel
- Butter and Margarine
How the Relationship Works
If the price of Good A goes up, the demand for Good B (its substitute) will increase.
The Logic: Consumers are smart! If the price of Beef rises, people will look for a cheaper alternative. They stop buying Beef and start buying Chicken instead. Therefore, the demand for Chicken goes up, even though the price of Chicken hasn't changed yet.
Memory Aid: Substitutes = Switch. If the price of one goes up, you Switch to the other.
Quick Takeaway: For substitutes, Price and Demand move in the same direction. (If Price A \(\uparrow\), then Demand B \(\uparrow\)).
2. Complements: The "Together" Goods
Complements are goods that are used together. They are like best friends—one isn't much use without the other. Economists sometimes call this joint demand.
Common Examples:
- Printers and Ink Cartridges
- Cars and Petrol/Diesel
- Games Consoles and Video Games
- Fish and Chips
How the Relationship Works
If the price of Good A goes up, the demand for Good B (its complement) will decrease.
The Logic: If the price of printers doubles, fewer people will buy printers. Because fewer people own printers, they won't need to buy ink. So, the demand for ink falls because the "main" product became too expensive.
Did you know? This is why some companies sell the main product (like a razor or a printer) very cheaply. They know that once you own it, you must buy the complements (blades or ink) for years to come!
Quick Takeaway: For complements, Price and Demand move in opposite directions. (If Price A \(\uparrow\), then Demand B \(\downarrow\)).
3. Step-by-Step: How One Market Changes Another
In your exam, you might be asked to explain the "impact" of a change. Let's look at a real-world chain of events. Don't panic—just follow the arrows!
Scenario: The Price of Coffee Rises (Substitutes)
1. The price of Coffee increases.
2. Consumers react to the higher price by buying less coffee (movement along the demand curve).
3. Because Tea is a substitute, consumers switch their spending to Tea.
4. The Demand Curve for Tea shifts to the right (an increase in demand).
5. This extra demand in the Tea market might then cause the price of Tea to rise too!
Scenario: The Price of Smartphones Falls (Complements)
1. The price of Smartphones decreases.
2. More people buy smartphones because they are cheaper.
3. Because Mobile Apps are a complement, people now need more apps for their new phones.
4. The Demand Curve for Apps shifts to the right.
4. Summary Table for Quick Review
Relationship: Substitutes (Competitive Demand)
Definition: Goods used instead of each other.
Price of A \(\uparrow\): Demand for B \(\uparrow\)
Example: iPhone vs. Samsung
Relationship: Complements (Joint Demand)
Definition: Goods used together.
Price of A \(\uparrow\): Demand for B \(\downarrow\)
Example: Cinema tickets and Popcorn
5. Common Mistakes to Avoid
Mixing up the terms: Students often confuse the two. Just remember: Complements Complete each other.
Focusing on the wrong "Demand": When the price of Coffee rises, the Quantity Demanded for Coffee falls (a movement), but the Demand for Tea shifts (a shift). Make sure you distinguish between the two markets!
Forgetting the "Why": Always explain the link. Don't just say "Demand for B goes up." Say "Because consumers switch to a cheaper alternative."
Final Check: Can you answer these?
- If the price of tennis rackets goes down, what happens to the demand for tennis balls? (Hint: They are complements!)
- If a new study says Strawberries are better for you than Raspberries, what happens to the market for Raspberries? (Hint: They are substitutes!)
Key Takeaway: Markets are interconnected. A change in price, supply, or demand in one market will create a "knock-on" effect in any market that sells a substitute or a complementary good. Mastering these links is the secret to thinking like a true economist!