Supply and Demand: The Invisible Seesaw
Why does a bottle of water cost $2 at the supermarket but $6 at a concert? Why do flights get more expensive during school holidays? Why did PlayStation 5 consoles sell for double the price when they first came out?
The answer is the most fundamental concept in economics: supply and demand.
The Two Forces
Demand is how much people want something. Supply is how much of it is available. The price is determined by the balance between these two forces.
- High demand + Low supply = Prices rise (concert tickets, new consoles, housing in Sydney)
- Low demand + High supply = Prices fall (last season's fashion, day-old bread, flights in off-peak season)
- High demand + High supply = Stable prices (basic groceries, petrol in normal times)
Real Australian Examples
Housing
Australia builds approximately 170,000 new homes per year but population grows by ~400,000 (ABS, 2023). Demand outstrips supply. Result: median house prices in Sydney hit $1.4 million by 2024 (CoreLogic).
Lettuce Crisis (2022)
Floods in Queensland destroyed lettuce crops. Supply crashed. Prices jumped from $2 to $12 per head. KFC temporarily replaced lettuce with cabbage in their burgers. When supply recovered, prices dropped back.
Petrol Prices
When OPEC (a cartel of oil-producing countries) cuts oil production, global supply falls and Australian petrol prices rise — even though Australia's demand hasn't changed.
When Supply and Demand Is Manipulated
The textbook version of supply and demand assumes a "free market." But markets are often manipulated:
- Monopolies control supply (one company dominates)
- Cartels fix prices (companies secretly agree not to compete)
- Artificial scarcity (limiting supply to keep prices high — diamonds are a classic example)
- Speculation (investors buy assets not to use but to resell at higher prices, driving up costs for everyone)
Tonight's Question
"Why do you think houses in Australia cost so much? Is it purely supply and demand, or is something else going on?"
Discuss: What could be done to make housing more affordable? Who benefits from high house prices? Who suffers?
The Auction Game
Need: Play money, 10 small objects, 3+ players.
- One person is the auctioneer with 10 items to sell.
- Give each player $100 in play money.
- Auction items one at a time — highest bidder wins.
- Now repeat with only 3 items. Watch how prices change.
- Now give each player $200 and auction the same 3 items. What happens to prices?
You've just demonstrated supply and demand AND inflation (more money chasing the same goods).
Go Further
- Research: Why are diamonds expensive? (Hint: look up De Beers and artificial scarcity.)
- Current events: What's happening to grocery prices in Australia right now? What's driving the changes?
- Book: Economics in One Lesson by Henry Hazlitt (1946, still relevant).
- Question: Should governments set maximum prices on essential items like food and rent?
What We Simplified
- Supply and demand is a model, not a perfect description. Real markets are messy, with government regulations, subsidies, taxes, and imperfect information.
- Housing is more complex than supply/demand alone. Tax policy (negative gearing, capital gains discounts), foreign investment, zoning laws, and credit availability all play roles.
- Prices carry information. High prices signal where resources are needed — this is actually useful in a market economy, even when it feels unfair.
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