IB Economics Diagrams: Drawing for Full Marks

The IB's economics guide assesses diagrams under the same criteria as written analysis — accuracy and relevance. Examiners marking paper 1 and paper 2 essays look for diagrams that are fully integrated into your argument, not bolted on as decoration.

Quick tip: Draw your diagram before you write the paragraph explaining it. Students who diagram first tend to structure their explanation around what's actually on the page, rather than describing a diagram that doesn't match what they drew.

This is why a diagram with no accompanying explanation often scores lower than one with a short paragraph pointing to it — examiners need you to use the diagram, not just include it.

Common mistake: drawing a diagram in the margin and never mentioning it in the text. If the examiner has to guess why it's there, it isn't doing its job.

Checklist before you move on from any diagram:

1. Both axes labelled with the correct variable and units
2. Original curves drawn first, in a different style/colour from any shift
3. Shift drawn as a new curve, not an edited original
4. New equilibrium point marked with dashed lines to both axes
5. Diagram title identifies what it shows (e.g. 'Effect of a subsidy on the market for rice')

Worked example: A government imposes a per-unit subsidy on rice producers. Draw original S and D curves crossing at P1, Q1. The subsidy shifts supply right to S2 (parallel shift, since it's a per-unit subsidy), creating a new equilibrium at P2, Q2 where P2 < P1 and Q2 > Q1. Label the vertical distance between S and S2 as the subsidy per unit — that vertical gap is what examiners check for.

A common error is drawing a steep demand curve and calling it 'inelastic' with no numbers attached. Examiners want to see that you understand elasticity as a ratio (%ΔQd / %ΔP), so add at least two price-quantity coordinate pairs to any elasticity diagram.

Worked example — negative production externality: Draw MPC and MSC as separate upward-sloping lines, with MSC above MPC (since social cost exceeds private cost). Demand (MPB=MSB) is a single downward line. Market equilibrium sits where MPC meets demand at Qm; the social optimum is where MSC meets demand at Qopt (Qopt < Qm). Shade the triangle between MPC, MSC and demand, between Qopt and Qm, as the welfare loss from overproduction.

Keynesian AS curves have a distinctive shape — flat, then upward-sloping, then vertical at full employment output — while the monetarist/new classical LRAS is a single vertical line at potential output (Yfe). Using the wrong AS shape for the model you're discussing in your essay is a frequent reason strong written analysis still loses diagram marks.

Pencil is fine for diagrams even in a pen-only exam, since diagrams are often the one part of the paper where a rough sketch benefits from being erasable. Check with your school's exam coordinator on local rules before the exam season.

Quick tip: if a diagram doesn't change once you've drawn it, ask whether it's actually adding analysis or just repeating what your first diagram already showed. A second diagram should show movement — a shift, a new equilibrium, a comparison — not the same static picture again.

On RevisionPrep, our topical worksheets for IB Economics include diagram-specific practice questions with model diagrams alongside written mark schemes, so you can compare your labelling and shading directly against what examiners expect.

This is one reason diagram practice is worth as much exam-prep time as essay writing itself — it's a skill, not decoration, and it's assessed every single paper.

RevisionPrep's revision notes for IB Economics include labelled model diagrams for every major topic, which gives your child something concrete to compare their own drawing against without needing you to check the economics content.