IB Economics SL & HLTopic 5 — Exam Skills and AssessmentPapers 1, 2 & 3Exam technique~9 min read
Scoring Full Marks on 4-Mark Questions
A 4-mark question sits in the awkward middle: too big for a one-line answer, too small for an essay. What the examiner wants is a chain — this causes that, which causes the other — and sometimes a diagram to carry it. Get the chain right and four marks is a quick, comfortable win.
📚 What you need to know
4-mark questions mostly test AO2: applying theory and analysing a relationship, plus AO4 when a diagram is asked for.
Marks come from correct economic reasoning and clear development of that reasoning.
One or two short, well-built paragraphs is the right size.
Only draw a diagram if the question asks for one — or if it genuinely carries the explanation.
If a diagram is required, it must be correct, fully labelled and referred to in your words.
Evaluation is not wanted. No “however”, no conclusion about whether the policy is good.
Always check which variable the question names. Explaining the wrong one scores zero however good it is.
The chain is the answer
Think of a 4-mark answer as four links. Each link is a step, and each step follows from the one before it. If a reader can trace your sentences from the trigger to the outcome without jumping, you have done what the question asked.
Write the chain out in the margin before you start. Then each sentence has a job.
The word that earns marks in a 4-mark answer is “so”. Incomes rise, so demand for a normal good rises, so there is a shortage at the old price, so the price is bid up. If you can say your answer with three “so”s, you have a chain.
When the question asks for a diagram
“Explain using a diagram” is an instruction, not a suggestion. A missing or badly labelled diagram can cost up to half the marks even when the written explanation is good.
This is the level of labelling expected. A diagram with unlabelled axes cannot earn full diagram marks, however neat it looks.
Refer to the diagram by its labels. “Demand shifts from D1 to D2, raising equilibrium price from P1 to P2” is worth far more than “as the diagram shows, price goes up”.
How to structure the answer
🧩 A reliable 4-mark structure
One short opening line naming the relationship, and defining a key term if it needs it.
The chain, in order, with a “so” or “therefore” between each step.
The diagram, if asked for, labelled fully.
One closing line that answers the exact variable in the question.
Worked examples
WORKED EXAMPLE
Explanation without a diagram
Explain how a rise in the national minimum wage may affect unemployment. [4]
Step 1: name the variable
The question is about unemployment, not wages or poverty.
Step 2: build the chain
minimum wage set above the equilibrium wage → labour costs more for firms → firms demand fewer workers → more people want to work at the higher wage → quantity of labour supplied exceeds quantity demanded.
Step 3: close on the variable
That excess supply of labour is unemployment, so unemployment is likely to rise.
4/4No “however it depends” — that would be evaluation, which is not asked for here.
WORKED EXAMPLE
Explanation using a diagram
Explain, using a diagram, how an increase in consumer incomes affects the market for a normal good. [4]
Step 1: define quickly
A normal good is one whose demand rises as income rises.
Step 2: draw and label
Demand and supply axes, S, D₁ shifting right to D₂, both equilibria marked.
Step 3: explain the diagram in words
Higher income raises willingness and ability to buy, so demand shifts right from D₁ to D₂. At the old price there is now a shortage, so price is bid up from P₁ to P₂, and quantity rises from Q₁ to Q₂.
4/4The diagram and the words do the same job twice — that is exactly what the mark scheme wants.
💡 Exam tip
Sketch the chain in the margin first. Four arrows, ten seconds, no wasted sentences.
Read the question twice for the variable — price, quantity, unemployment, revenue, output. Answer that one only.
Use subscript labels (D1, D2, P1, P2) so you can point at the diagram in your writing.
Keep it to one or two paragraphs. Four marks does not need a page.
If no diagram is asked for, do not draw one unless it saves you writing.
Finish with the outcome, clearly stated. Do not leave the examiner to infer it.
⚠ Common mix-up
Adding evaluation or a conclusion about whether the outcome is good. It is not asked for.
Skipping the middle of the chain and jumping from cause straight to result.
Drawing an unlabelled or half-labelled diagram and losing the technical marks.
Never mentioning the diagram in the writing.
Explaining the wrong variable — the most expensive mistake on the page.
Shifting the wrong curve. A change in income moves demand; a change in costs moves supply.
Up next: Working Through Calculation Questions — where the marks are hiding in the method, not the final number.
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