A graph answer earns credit when every sentence points back at the question. Describing the diagram is the start, and the marks usually sit in the sentence that says what the change means for what was asked.
The fix is a three-part sentence pattern that you can apply to any supply and demand diagram.
What does the problem look like?
Fictional question: Explain why the price of mangoes at a local market rose in June. The diagram shows supply moving left from S1 to S2. Price rises from RM6 to RM8 per kg. Quantity falls from 500 kg to 400 kg.
A student writes: “The graph shows that supply shifts left from S1 to S2. The price goes up from RM6 to RM8 and the quantity goes down from 500 to 400.”
Every fact is correct. But the question asked why, and the answer only says what.
A pattern to relate the graph to the question
Use three parts in order:
- What the diagram shows: the movement or shift, with values.
- Why it happened: the cause in the context of the question.
- What it means for the question: the result the question asked for, with the link word “so” or “because”.
Keep the command word in view: “Explain why” wants cause and “Describe” wants the pattern. “Analyse” wants the chain of reasons.
Worked example
Question: Explain why the price of mangoes rose in June.
Part 1, show: supply shifts left from S1 to S2. At the old price of RM6, quantity supplied is below quantity demanded.
Part 2, why: a fictional storm in May damaged mango trees, so growers could supply fewer kilograms at every price.
Part 3, link to the question: there is a shortage at RM6, so buyers compete, and the price rises to the new equilibrium of RM8. The rise is 2 on a base of 6, which is about 33%.
Finish with the movement along demand: as the price rises, quantity demanded falls along the demand curve, from 500 kg to 400 kg. It is a movement along the curve, not a shift of demand.
The full answer: “A storm reduced the mango harvest, so supply shifted left from S1 to S2. At RM6 there was a shortage, which pushed the price up to RM8, an increase of about 33%. The higher price reduced quantity demanded along the demand curve to 400 kg.”
Notice that the answer never uses the word “graph”. The diagram supports the answer instead of becoming the answer.
The mistake to watch for
Mistaken answer: “The graph shows that the price goes up because the curve moves.”
The phrase “the curve moves” is what the picture shows, not a reason. Ask “what made the curve move?” and put that in the sentence. The word “because” must be followed by something in the real world, not something on the page.
A self-check you can do alone
Before you move on, tick these:
- Did I use the question’s own words, such as the product and the month?
- Is there a reason in the real world, not only on the diagram?
- Did I say whether it was a shift or a movement along a curve?
- Did I use the before and after values?
Try it: improve this sentence
Sentence: “The demand curve moves right and equilibrium price is higher.”
Question: Explain why the price of umbrellas rose in the rainy season.
Improved: “In the rainy season more people wanted umbrellas at every price, so demand shifted right. This created a shortage at the old price, which raised the equilibrium price.”
Try it: shift or movement?
Situation: the price of a fictional phone case falls from RM20 to RM15, and quantity sold rises from 100 to 130.
Answer: a fall in the product’s own price causes a movement along the demand curve (an extension in quantity demanded), not a shift. A shift would need a change in something else, such as income or tastes.
Where to go next
The supply and equilibrium module builds the diagrams, demand relationships explains the shift versus movement distinction in more depth, and Economics data responses practises the pattern on tables and charts. Use the percentage-base explorer to check the base when you quote a percentage change. The Economics study route shows where to place this practice.
If the pattern works alone but slips when you write fast, online one-to-one Economics tuition gives you a teacher who reads your sentences as you write them, starting with a paid one-hour trial lesson.