Demand and supply explains how prices and quantities settle in a market, and what moves them when conditions change. Most SPM Economics diagram questions start here.
This cluster is part of SPM Economics. It covers four skills, in the order you should learn them.
What does this cluster cover?
- Distinguishing movement along a curve from a shift sorts every change into one of two types.
- Drawing market equilibrium finds where demand and supply meet.
- Explaining changes in price and quantity writes the full reasoning chain after a curve shifts.
- Calculating and interpreting elasticity within syllabus scope measures how strongly quantity responds to price.
After these, price mechanism with more than one change handles questions where both curves move.
One short example: a movement and a shift
A fictional stall sells iced lemon tea. Buyers take 100 cups a day at RM2, and 80 cups a day at RM3.
If the stall raises the price from RM2 to RM3, buyers move along the same demand curve to 80 cups. Nothing else changed, so the curve did not move.
Now suppose a hot spell arrives and the price stays at RM3. Buyers now want 100 cups at RM3, because the weather changed their willingness to buy. The whole demand curve has shifted right.
| Event | Type | What happens to the curve |
|---|---|---|
| Stall’s own price rises | Movement | Same curve, new point |
| Hot spell | Shift | Whole curve moves right |
How do the parts connect?
Movement versus shift tells you what happened. Equilibrium shows where the market settles. The third lesson explains why price and quantity end up where they do, and elasticity measures how strong the response was.
If the first lesson is solid, the rest become routine. If it is not, every later diagram feels like guesswork.
Who should start where?
- Unsure which way a curve moves: start with movement versus shift.
- Can draw curves but cannot label equilibrium: start with drawing market equilibrium.
- Drawing well but writing short answers: start with explaining changes.
- Afraid of calculations: read elasticity last, with a calculator and two short worked examples.
Test yourself with the demand and supply practice set, and try the supply-demand diagram reasoning explorer. For a teacher to check your diagrams with you, see online one-to-one Economics tuition.