Demand

Welcome to the World of Demand!

Ever wondered why the price of strawberries drops in the summer, or why everyone suddenly wants the latest iPhone even if it costs a fortune? It all starts with Demand. In this chapter, we’re going to look at how consumers (that’s you!) make choices and what makes us want to buy more or less of something. Don't worry if it seems like a lot to take in at first—we'll break it down step-by-step!

1. The Starting Point: Rational Decision Making

Before we look at demand curves, we have to understand how economists think about people. We use a starting assumption called Rational Decision Making.

The Golden Rules of Rationality:

• Consumers (us) aim to maximise utility. "Utility" is just a fancy economics word for satisfaction or happiness. We want the most "bang for our buck."
• Firms (businesses) aim to maximise profits. They want to make as much money as possible after paying their costs.

Think of it this way: When you go to a shop with £5, you are trying to buy the combination of snacks that makes you the happiest. That is you "maximising your utility"!

2. What is "Demand"?

In Economics, demand isn't just "wanting" something. I might want a Ferrari, but if I can't afford it, I don't represent Effective Demand.

Effective Demand is the quantity of a good or service that consumers are willing and able to buy at a given price at a given time.

The Law of Demand

There is an inverse relationship between price and quantity demanded.
- When the Price (\( P \)) goes UP, the Quantity Demanded (\( Q_d \)) goes DOWN.
- When the Price (\( P \)) goes DOWN, the Quantity Demanded (\( Q_d \)) goes UP.

Quick Review: Why does the curve slope downwards?

One major reason is the Law of Diminishing Marginal Utility.
Imagine you are eating slices of pizza. The first slice is amazing (high utility). The second is good. By the fifth slice, you’re feeling a bit sick (low utility). Because each extra (marginal) unit gives you less satisfaction, you are only willing to buy more if the price drops!

Key Takeaway: Demand curves almost always slope downwards from left to right. As things get cheaper, we buy more.

3. Movements vs. Shifts (The Exam Trap!)

This is where many students lose marks, but it’s easy once you get the hang of it. You need to know the difference between moving along the line and moving the whole line.

Movements Along the Demand Curve

A movement only happens when the Price of the good itself changes.

• Extension in Demand: When the price falls, and we move down the curve to a higher quantity.
• Contraction in Demand: When the price rises, and we move up the curve to a lower quantity.

Memory Aid: If Price is the cause, the line stays in place!

Shifts of the Demand Curve

A shift happens when anything other than price changes. The whole curve moves left or right.

• Shift to the Right: An increase in demand (people want more at every price).
• Shift to the Left: A decrease in demand (people want less at every price).

Don't worry if this seems tricky! Just ask yourself: "Did the price of the item change?" If yes, it's a movement. If no, it's a shift.

4. Why does the Curve Shift? (Conditions of Demand)

To remember why a demand curve might shift, use the mnemonic PASIFIC:

P - Population: If there are more people (e.g., through migration), demand for basic goods like food and housing shifts right.

A - Advertising: A successful ad campaign makes a product more "trendy," shifting demand to the right.

S - Substitutes: These are "either/or" goods (like Pepsi vs. Coca-Cola). If the price of Pepsi goes up, the demand for Coke shifts to the right because people switch!

I - Income:
- For Normal Goods, as income goes up, demand shifts right (e.g., restaurant meals).
- For Inferior Goods, as income goes up, demand shifts left (e.g., basic "value" brand noodles, because you can now afford better stuff).

F - Fashion and Tastes: If something goes out of style (like fidget spinners), the demand shifts left.

I - Interest Rates: If interest rates rise, borrowing is more expensive. Demand for "big ticket" items bought on credit (like cars or sofas) shifts left.

C - Complements: These are "go together" goods (like printers and ink cartridges). If the price of printers falls, more people buy them, so the demand for ink cartridges shifts right!

Did you know? Sometimes a shift can be caused by expectations. If people think the price of gold will rise tomorrow, they will demand more of it today, shifting the current demand curve to the right!

Key Takeaway: Factors like Income, Tastes, and the Price of other goods cause the whole demand curve to shift. Price only causes a movement.

5. Common Mistakes to Avoid

1. Confusing "Demand" with "Quantity Demanded": "Demand" refers to the whole curve. "Quantity Demanded" is a specific point on that curve.
2. Mixing up Substitutes and Complements: Always double-check! A Substitute is a Switch (Coke for Pepsi). A Complement Completes the other (Fish and Chips).
3. Drawing arrows wrong: In an exam, always draw an arrow to show which way the curve shifted and label your new curve \( D_1 \).

6. Summary: Quick Review Box

Definition: Demand is the willingness and ability to buy a good at a given price.
The Curve: Slopes downwards due to diminishing marginal utility.
Movement: Caused ONLY by a change in the price of the good itself.
Shift: Caused by non-price factors (PASIFIC).
Rationality: We assume consumers try to get the most satisfaction (utility) possible.

You've finished the notes on Demand! Next, we'll look at Supply to see how these two forces meet to create market prices. You're doing great!