← Market structures and marginal analysis
Annotating the graph: what to label, shade, and name
A large share of the marks on this standard are earned directly on the diagram, before you write a word of explanation — knowing exactly what to shade and label is a skill in its own right.What a complete annotation includes
- The profit-maximising price and quantity, each labelled with a letter matching the question (P₁, Q₁, Pmc, Qmc, etc.) — never leave a point unlabelled even if it looks obvious.
- Consumer surplus, shaded as the triangle between the demand curve and the price, up to the quantity sold.
- Deadweight loss, shaded as the triangle between demand and marginal cost, beyond the quantity actually produced — and stated explicitly if none exists (e.g. under marginal-cost pricing).
- Economic profit or loss, shaded as the rectangle between price and average cost, across the quantity produced.
- Any SHIFTED curve, drawn as a new curve with its own label (MC₁, AR₁) — never redraw over the original without labelling both.
Shading without labelling what the shaded area represents
Shading the correct area on a graph earns little if it is not labelled — a marker needs to see the word "consumer surplus" or "deadweight loss" attached to the shape, not just correctly-placed shading. Always write the name of what you have shaded next to it.A fast check before moving from the graph to the written answer
- Is every point I use in my writing also labelled on the diagram?
- Have I named every shaded area, even the ones that seem obvious?