Welcome to Demand and Supply!

Ever wondered why the price of strawberries drops in the summer or why the latest gaming console is so expensive when it first launches? The answer lies in Demand and Supply. This is one of the most important chapters in your Business AS Level because it explains how the "External Environment" (the world outside the business) dictates the prices a business can charge and how much they should produce.

Don't worry if the graphs look intimidating at first. By the end of these notes, you’ll be reading them like a pro! Let's dive in.

1. What is Demand?

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

The Law of Demand: Generally, as the price of a product increases, the quantity demanded falls. As the price decreases, the quantity demanded rises. There is an inverse relationship between price and demand.

Determinants of Demand (The 'Shift' Factors)

Sometimes, demand changes even if the price stays the same. This is called a "shift" in the demand curve. Think of the mnemonic PASIFIC to remember what causes these shifts:

  • P - Population: More people usually means more demand.
  • A - Advertising: A successful campaign makes people want the product more.
  • S - Substitutes: If the price of a rival product (like Pepsi) goes down, demand for the substitute (like Coca-Cola) might fall.
  • I - Income: When people earn more, they tend to spend more on most goods.
  • F - Fashion and Tastes: If a product becomes "trendy," demand sky-rockets!
  • I - Interest Rates: If it's cheaper to borrow money, people might buy expensive items like cars on credit.
  • C - Complements: These are goods bought together (like printers and ink). If the price of printers drops, demand for ink goes up.
Quick Review:

Movement along the curve: Caused ONLY by a change in the price of the product itself.
Shift of the curve: Caused by any factor OTHER than the price (like a change in income).

2. What is Supply?

Supply is the quantity of a good or service that a producer is willing and able to provide to the market at a given price.

The Law of Supply: As the price of a product increases, the quantity supplied usually increases. Why? Because higher prices mean higher potential profits for the business, so they want to sell more!

Determinants of Supply (Why the curve shifts)

Supply shifts when it becomes easier, harder, cheaper, or more expensive to produce the goods. Key factors include:

  • Costs of Production: If wages or raw material prices go up, supply shifts left (decreases) because it’s more expensive to make the product.
  • Technology: New machinery makes production faster and cheaper, shifting supply right.
  • Taxes (Indirect): If the government increases taxes on a product (like cigarettes), it's like an extra cost for the business, so supply decreases.
  • Subsidies: This is "free money" from the government to help businesses. This reduces costs and increases supply.
  • External Shocks: Things like bad weather (destroying crops) or wars can significantly reduce supply.
Key Takeaway:

Think of supply from the business owner's perspective. If it gets cheaper or easier to make something, you'll want to supply more!

3. Market Equilibrium

Equilibrium occurs at the price where the quantity demanded by consumers exactly matches the quantity supplied by producers. On a graph, this is exactly where the Demand (D) and Supply (S) curves cross.

At this point, the market is "cleared"—there are no frustrated buyers and no unsold stock. The price at this point is called the Equilibrium Price, and the quantity is the Equilibrium Quantity.

How Equilibrium Changes

When a determinant of demand or supply changes, the curves shift, and a new equilibrium is created. Let’s look at two common scenarios:

Scenario A: Demand Increases (e.g., a product becomes fashionable)
  1. The Demand curve shifts to the right.
  2. The new equilibrium point will be at a higher price and a higher quantity.
Scenario B: Supply Decreases (e.g., raw material costs rise)
  1. The Supply curve shifts to the left.
  2. The new equilibrium point will be at a higher price but a lower quantity.

Don't worry if this seems tricky! Just remember: A shift to the Right is an increase, and a shift to the Left is a decrease (Left = Less).

4. Excesses and Shortages

What happens if the price is NOT at the equilibrium? We get an imbalance in the market.

Excess Supply (A Surplus)

This happens when the price is set above the equilibrium level.
Analogy: Imagine a shop charging £100 for a simple t-shirt. Lots of businesses want to sell them (High Supply), but nobody wants to buy them (Low Demand).
Result: Shelves are full of unsold stock. To fix this, the business must lower the price until it reaches equilibrium.

Excess Demand (A Shortage)

This happens when the price is set below the equilibrium level.
Analogy: A shop sells the latest iPhone for only £5. Everyone wants one (High Demand), but the manufacturer can't make any profit at that price, so they only make a few (Low Supply).
Result: Long queues and empty shelves. To fix this, the business can raise the price because they know customers are willing to pay more.

Quick Review Box:
  • Price too high? = Surplus (Supply > Demand)
  • Price too low? = Shortage (Demand > Supply)

5. Impact on Business Decisions

Understanding demand and supply helps a business make two major decisions:

  1. Price Decisions: If demand is high and supply is low (like tickets for a Taylor Swift concert), a business can charge a very high price.
  2. Output Decisions: If the costs of production fall (supply increases), a business might decide to produce a larger quantity to grab more market share.

Did you know? Businesses spend millions on market research just to try and predict how the Demand curve will shift so they can be ready with the right amount of stock!

Summary Checklist

Make sure you can:

  • Define demand, supply, and equilibrium.
  • List at least 3 factors that shift demand and 3 that shift supply.
  • Draw a basic D/S diagram and show what happens when a curve shifts.
  • Explain why a surplus happens when prices are too high.

Common Mistake to Avoid: Don't confuse a "movement along the curve" with a "shift." If the price of the product changes, you just move your dot along the existing line. If anything else changes (like income or costs), you must draw a whole new line!