Graph construction
- Syllabus
- 2026
- Topic
- —
- Level
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Learning objectives
Construct accurate economic graphs from data
A graph converts numerical relationships into a visual form. A correct economic graph must preserve the data, variables, units and scale before any interpretation is added.
| Step | Construction decision | Check |
|---|---|---|
| 1 identify variables | decide what each axis measures; independent/category variable usually on x, measured outcome on y | names and units match the data |
| 2 choose graph type | line for change over continuous time; bar for categories; scatter for paired observations; supply/demand for price–quantity schedules | type fits the relationship |
| 3 choose scale | cover the full range with equal numerical intervals | no distorted or unexplained break |
| 4 plot | mark every coordinate accurately | x and y values read from the same row |
| 5 connect/represent | join ordered time or curve points appropriately; keep categories separate in bars | no invented intermediate values |
| 6 label | title, axes, units, curves and relevant equilibrium | another reader can identify every element |
For supply and demand data, put price on the vertical axis and quantity on the horizontal axis. Plot demand and supply schedules, label D and S, and mark their intersection as equilibrium price and quantity. Do not assume straight lines if the plotted data do not support them.
Read two or more plotted points back from the graph and compare them with the source table. Check that a larger plotted movement represents a genuinely larger numerical movement under the chosen scale.
Constructing a graph is not the same as explaining it. First reproduce the data accurately; then use direction, gradient, turning points or equilibrium for interpretation only when asked.