IB Economics SLTopic 5 — Assessment and Exam SkillsPaper 2Exam skill~7 min read
Writing a Strong 4-Mark Answer
Four marks is an awkward size. It is too big for one line and far too small for an essay, and that is exactly where people lose marks: they either stop after a statement or they write for ten minutes and drift into evaluation nobody asked for. The fix is knowing what four marks actually buys.
📘 What you need to know
A 4-mark question sits between a short factual answer and a developed analytical one. It is mostly AO2, and AO4 as well when a diagram is asked for.
Examiners want a clear explanation of an economic relationship, using theory, a diagram or data as required.
Marks come from correct reasoning and developed explanation: a chain, not a statement.
The usual command terms are explain, explain how and explain using a diagram.
Draw a diagram only if the question asks for one, and then refer to it in your writing.
Read the question for which variable you must end on. Explaining the wrong variable scores nothing.
No evaluation. There are no marks for judgement at this size.
What four marks is asking for
Think of the marks as steps in a chain rather than four separate facts. You start with the change the question gives you, explain the economics that links each step to the next, and land on the exact variable named in the question. Each new link is where a mark comes from; repeating the same idea in different words is not a new link.
Most 4-mark answers that score two marks are correct economics that stopped one link too early.
The three command terms and what they change
explain = describe the relationship using theory • explain how = cause and effect, step by step • explain using a diagram = the diagram is compulsory
🧩 The routine for any 4-mark question
Find the variable the question wants you to end on. Underline it.
Check for the word “diagram”. If it is there, draw one. If it is not, do not.
Write the chain in order, with a “because” or a “so” between each step.
Use the terminology. “Quantity demanded contracts” beats “people buy less” every time.
Stop. No evaluation, no conclusion, no “in my opinion”.
WORKED EXAMPLE
Explain how a rise in income tax may affect consumer spending. [4]
Step 1: name the variable to land on
Consumer spending. Every sentence has to be walking towards it.
Step 2: no diagram is asked for, so do not draw one
Two or three sentences is the right size here.
Step 3: write the chain
A rise in income tax reduces households’ disposable income, because a larger share of gross income is taken by the government. With less disposable income, households can afford fewer goods and services at each price level, so consumption falls. Since consumption is the largest component of aggregate demand, total spending in the economy is likely to fall.
Four links, four marksThe word “because” is doing the work. Take it out and the paragraph turns back into a list of statements.
When the question says “using a diagram”
Those three words turn the question into an AO4 question as well. A diagram that is wrong or badly labelled can cost up to half the marks even when the writing is fine, so keep it simple, accurate and relevant: axes labelled, curves named, original and new equilibrium marked. Then point at it in words. A diagram nobody refers to is treated as decoration.
The vertical gap between the two supply curves is the tax per unit. Showing it costs nothing and proves you know what the shift represents.
WORKED EXAMPLE
Explain, using a diagram, how an indirect tax on producers affects the price and quantity of a good. [4]
Step 1: the diagram first
Demand and supply, axes labelled P/unit and Q/period, S1 shifting left to S2 by the size of the tax, P1, P2, Q1, Q2 marked.
Step 2: the written chain, pointing at the diagram
An indirect tax raises the cost of producing each unit, so firms are willing to supply less at every price and supply shifts left from S1 to S2. At the original price P1 there is now excess demand, so price rises to P2 and quantity falls to Q2, as shown on the diagram.
Step 3: check the variables named in the question
Price: covered. Quantity: covered. Both are stated with their labels.
Diagram + explicit reference = full marks“As shown on the diagram” is a small phrase that earns real credit. Use it once, properly.
If you finish a 4-mark answer and it is half a page long, something has gone wrong. Either you have written an introduction nobody wanted, or you have started evaluating. Both cost you time you need later in the paper.
💡 Exam tip
Count your links before you move on. Four marks, roughly four steps in the chain.
Use “because” and “so” deliberately. They force development into the writing and stop you listing.
Draw the diagram big enough to label. Half a page is plenty; a tiny sketch loses labels.
Refer to your diagram in the text at least once, using the labels you wrote on it.
If data is provided, use a figure from it even in a short answer. It costs one clause and proves application.
Keep the timing honest. At Paper 2 pace, four marks is around ten minutes including the diagram.
⚠️ Common mix-up
Adding evaluation or a conclusion. There are no AO3 marks here, so it is unpaid writing.
Drawing a diagram that was not asked for. It takes minutes and adds nothing to the mark.
Leaving axes or curves unlabelled. When the diagram is required, poor labelling can cost up to half the marks.
Explaining the wrong variable. A perfect answer about price scores nothing if the question asked about output.
Restating the same point in new words and hoping it counts as development. It does not.
Never mentioning the diagram in the writing, so the examiner cannot link the two.
Up next: Getting Calculation Questions Right — where method marks are available even when the final number is wrong, and where units and signs quietly decide your score.
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