IB Economics HL onlyTopic 5 — Exam Skills and AssessmentPaper 3Calculation skill~9 min read
Working Through Paper 3 Questions
Paper 3 has a logic you can rely on. Everything you calculate in part (a) becomes the evidence for the recommendation in part (b). Students who treat the two halves as unrelated do all the hard work and then throw away the marks it was supposed to earn.
📚 What you need to know
Part (a) is a run of short quantitative tasks. Part (b) is a 10-mark policy recommendation.
Part (b) must build directly on part (a). Answers that ignore the earlier numbers cannot reach the top bands.
Recommend one policy. Listing several reduces depth and weakens the evaluation.
Paper 3 is not an essay paper: long generic writing with no quantitative support loses serious marks.
Examiners reward the progression data → analysis → policy.
Diagrams should be used analytically, not decoratively, and must be explained.
Leave enough time to plan, evaluate and conclude — rushed evaluation is the classic weakness here.
Part (a) is the evidence bank
Each small answer you produce is a fact you own. By the time you reach part (b) you should have a short list of numbers — a rate, a balance, a multiplier, an elasticity — that nobody can argue with, because you calculated them from the data provided.
The paper is designed as one journey. Marking it as three separate stages is how students lose the top bands.
The five moves of a 10-mark recommendation
Decide the policy in the first minute. The rest of the time is for proving it, not for changing your mind.
The best part (b) answers sound almost like advice to a finance minister: here is what I would do, here is why the numbers support it, here is what could go wrong, and here is my recommendation anyway.
Worked examples
WORKED EXAMPLE
Part (a): using the multiplier
Country X has a marginal propensity to save of 0.15, a marginal rate of tax of 0.10 and a marginal propensity to import of 0.05. The government plans to raise spending by $6 billion. Calculate the multiplier, and the change in national income. [4]
Step 1: formula for the multiplierk = 1 ÷ (MPS + MPT + MPM)Step 2: substitutek = 1 ÷ (0.15 + 0.10 + 0.05) = 1 ÷ 0.30 = 3.33Step 3: change in incomeΔY = k × ΔG = 3.3333… × 6 = 20.00k = 3.33 and ΔY = $20.00 billionRound only the value you report. If you multiply by the rounded 3.33 you get $19.98bn — close, but not what the mark scheme has.
WORKED EXAMPLE
Part (b): building the recommendation on those numbers
Using information from the text and data, recommend a policy the government of Country X could use to reduce unemployment. [10]
Move 1: name one policy
Expansionary fiscal policy, through government spending on labour-intensive infrastructure.
Move 2: how it works
Higher government spending raises aggregate demand → firms increase output → they hire more workers → cyclical unemployment falls.
Move 3: my own numbers
The multiplier is 3.33, so the $6bn injection raises national income by about $20bn. The data also shows unemployment is concentrated among low-skilled workers, which construction work suits.
Move 4: limits
A larger budget deficit and rising public debt; time lags in planning and building; some spending leaks abroad, which is why MPM matters.
Move 5: judgement
With a multiplier above 3 and spare capacity in construction, the employment gain is likely to outweigh the short-run cost, so I recommend the infrastructure spending.
10/10 shapeEvery claim is anchored either to the data or to a figure I calculated myself.
💡 Exam tip
Keep a results list in the margin as you work through part (a). It becomes your evidence bank.
Choose the policy that your numbers support, not the one you know most about.
Quote your own figures in part (b), with units. “The multiplier of 3.33” is far stronger than “a large multiplier”.
Refer back to any diagram you drew earlier rather than drawing it again.
Name real constraints from the data: the size of the deficit, the exchange rate, spare capacity, the inflation rate.
Reserve about 12 minutes per part (b) so the evaluation and judgement are not squeezed.
Stay in the context. The answer is about this country, in this situation, with these numbers.
⚠ Common mix-up
Recommending two or three policies to seem balanced. It caps the mark.
Writing a general essay about fiscal policy with no numbers in it.
Ignoring part (a) entirely, which is the single most common reason a strong writer scores in the middle bands.
Only listing advantages and calling it a recommendation. Limits are part of the marks.
Ending without a decision. “Both approaches have merit” is not a recommendation.
Rounding at every step so the figure quoted in part (b) no longer matches part (a).
Leaving part (b) until the last five minutes, when 20 of the paper’s 60 marks live there.
That is the end of Topic 5. Up next: the syllabus topics themselves — pick the paper you find hardest, take one past question, and rebuild your answer using the structures from these pages.
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