The AS91399 answer machine
What this paper actually asks
Three questions, all attempted, and each one climbs the same staircase:
- Do something to the graph — add a curve, identify a price and quantity, shade and label an area, or complete a table matching letters to CS, PS, revenue and DWL.
- Explain one change, with the instruction "refer to Graph One".
- Explain the impact on consumers, producers, the Government, and allocative efficiency — usually as four headed sections.
- Compare and contrast, or explain which impact is greater. This is the Excellence part and it is always last.
The four-participant template
Nearly every question in this standard can be answered with the same four blocks. Learn them as a shape.
Consumers
- Direction of the price they pay: from Pe to ___
- Direction of the quantity they buy: from Qe to ___
- Therefore consumer surplus rises / falls, for both reasons — the offset between price and quantity.
Producers
- Direction of the price they receive: from Pe to ___
- Direction of the quantity they sell: from Qe to ___
- Therefore producer surplus rises / falls, and say whether the two effects reinforce or oppose each other.
The Government
- Does it gain revenue (tax, tariff), pay out (subsidy), or get nothing (price control, quota)?
- Give the rectangle: height × width, and be exact about the width.
Allocative efficiency
- Where is the deadweight loss triangle? Between ___ and ___
- Why do those trades no longer happen? Because over that range demand lies above supply (or supply above demand).
- Therefore total surplus is no longer maximised and the market is allocatively inefficient.
The anchor-point rule
The Assessment Reports use one phrase repeatedly to describe Excellence answers: they integrate the graph by quoting anchor points.
| Weak | Strong |
|---|---|
| "The price went up" | "The price consumers pay rose from Pe to Pc" |
| "Fewer are sold" | "Quantity fell from Qe to Q1" |
| "Consumers lose out" | "Consumer surplus falls by the area between Pe and Pc out to Q1, plus the triangle between Q1 and Qe" |
| "There is inefficiency" | "A deadweight loss triangle appears between Q1 and Qe, so total surplus is no longer maximised" |
- Every number, letter and label printed on the graph is there to be quoted back. If the graph names an area A, B or C, use those letters.
Compare and contrast: the sentence patterns
Excellence asks you to compare and/or contrast the impacts on different participants. That means putting them side by side in one sentence, not describing them one after another.
- "Whereas ___, ___." — "Whereas consumers pay $1.00 more per unit, producers keep only $0.50 less, so consumers bear two thirds of the tax."
- "Both ___, but ___." — "Both consumers and producers lose surplus, but consumers lose more because demand is inelastic, so the price rise Pc − Pe is larger than the price fall Pe − Pp."
- "The larger impact is on ___ because ___." — "The larger impact falls on producers, because with elastic demand they cannot pass the tax on."
- "The same ___, but a different ___." — "A quota and a tax produce the same quantity and the same deadweight loss, but a different recipient for the middle rectangle."
What the Assessment Reports say costs marks
Straight from the 2024 and 2025 Not Achieved lists:
- Did not calculate values from the graph, or calculated them wrongly.
- Did not correctly interpret or draw the graphs.
- Identified a change but gave no reason for it.
- Did not refer to the graph or table in the explanation.
- Used demand and quantity demanded interchangeably.
- Did not use the mechanism of market forces to explain how equilibrium is restored.
- Included a definition but did not apply it to the context.
Worked ExampleTurning a bare answer into a Merit answer, then an Excellence answer
A $3 per unit tax is imposed on an illustrative market. Pe was $10 and Qe was 4,000 units. After the tax, Pc = 9 and Q1 = 3,000 units.
Explain the impact of the tax on consumers and on producers.
The bare answer — Achieved at best
"Consumer surplus falls because the price goes up. Producer surplus falls too because they get less money."
This identifies both directions and gives one reason each. It never quotes a single value from the graph, never mentions the quantity effect, and never compares the two.
Adding the graph and the second reason — now Merit
"Consumers. The price consumers pay rises from Pe = $10 to Pc = $12, so on each of the 3,000 units they still buy they pay $2 more. They also stop buying the 1,000 units between Q1 = 3,000 and Qe = 4,000, losing all the surplus they earned on those. Consumer surplus therefore falls for both reasons.
Producers. The price producers keep falls from Pe = $10 to Pp = $9, read down from Q1 to the original supply curve, so they lose $1 per unit on the 3,000 they still sell. They also lose the 1,000 units between Q1 and Qe. Producer surplus falls for both reasons."
Every claim now has an anchor point and every surplus change has the two-part reason. This is what "in-depth" means.
Adding the comparison — now Excellence
Add this paragraph on the end:
"Comparing the two. Both participants lose on price and on quantity, but the burden is not shared equally. Consumers absorb $2 of the $3 tax (Pc − Pe = $2) while producers absorb only $1 (Pe − Pp = $1), so consumers bear two thirds of it. The reason is relative elasticity: demand in this market is more inelastic than supply, so when producers raise the price, quantity demanded falls only from 4,000 to 3,000 — a fall of 25% for a 20% price rise. Because consumers keep buying, producers can pass most of the tax on. Had demand been elastic, consumers would have left the market instead, quantity would have collapsed, and the split would have reversed."
The comparison is now in the same sentences as the two participants, the graph is integrated, and the underlying cause is identified rather than asserted.