Explain demand, supply and price interactions
Identify influences on demand and supply, then explain how changing conditions can affect price and sales for a business.
Section 3.1 · The nature of marketing
Cambridge International AS & A Level Business 9609, 2026–2028 syllabus and 2029 syllabus, section 3.1.2. Cambridge states that the 2029 syllabus has no significant changes affecting teaching. This lesson maps only its named section; other sections and full paper practice remain separate. Written practice is self-checked
Before you begin
- No previous business course is assumed. Use the lesson's definitions before applying them to the business context.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which is most likely to shift demand for a product?
What you will learn
- Distinguish demand-side and supply-side influences
- Explain how demand and supply interact with price
- Apply a conditional price explanation to a business
Demand and supply have different drivers
Demand is influenced by customer incomes, preferences, the price and availability of substitutes or complements, population and expectations. A change in a product's own price usually changes quantity demanded; a change in another determinant can shift demand.
Supply can be influenced by input costs, productivity, technology, taxes, weather, capacity and the number of suppliers. A business should identify which condition changed before predicting an effect.
Price responds to the market situation, not a single rule
Where demand rises relative to available supply, sellers may face shortages or queues and may have scope to raise prices. Where supply expands relative to demand, competitive pressure may make lower prices or greater sales more likely. The result depends on competition, contracts, customer response and capacity.
For one firm, market conditions do not dictate its exact price. It must consider its costs, objectives and rivals. Higher prices can improve revenue per unit but reduce quantity demanded; lower prices can stimulate demand but squeeze contribution.
Pause and explain
A harvest failure reduces the supply of fresh strawberries while demand is stable. What pressure may result?
Worked example
A popular event raises demand for a local hotel while room capacity is fixed. Explain a likely interaction and a constraint on the hotel's decision.
Show the worked solution
- Demand has increased while short-run room supply is fixed.
- At the current rate, rooms may become scarce relative to bookings.
- The hotel may consider a higher rate but must account for rivals and customer response.
Answer The demand increase relative to fixed room capacity may create excess bookings at the current price, giving the hotel scope to raise rates. The hotel should consider nearby competitors, booking terms and how much higher prices may reduce bookings or damage reputation.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A substitute drink becomes more expensive. Explain a possible effect on demand for a café's iced tea and one limit to the prediction.
Give me a hint
Connect the relative price change to customer substitution, then qualify it.
Compare my reasoning
- The substitute's price has risen.
- Some customers may switch to iced tea, shifting its demand outward.
- The effect depends on preferences, availability and how close the substitute is.
If customers see iced tea as a substitute, some may switch to it, increasing demand at each iced-tea price. The size of the effect depends on how closely customers view the drinks and whether iced tea is available and appealing.
Look for these in your work
- Demand-side change is identified
- Likely direction is explained
- Prediction is qualified
A manufacturer improves productivity while demand is unchanged. Explain a possible supply effect and a pricing choice.
Give me a hint
Separate the cost or capacity change from the firm's final decision.
Compare my reasoning
- Higher productivity can lower unit costs or free capacity.
- Supply may increase if the firm chooses to produce more.
- The firm could keep price, cut price or invest savings; objectives and competition matter.
Higher productivity may reduce unit cost or release capacity. If the manufacturer increases output, market supply may rise and put pressure on price, but the firm could instead hold price and seek margin or use the savings for quality; its choice depends on objectives and rivals.
Look for these in your work
- Productivity mechanism is given
- Supply effect is conditional
- A pricing choice is evaluated in context
A competitor cuts price during a period of weak demand. Explain two factors your business should examine before matching it.
Give me a hint
Think about customer response and whether the lower price covers the firm's economics.
Compare my reasoning
- Estimate whether customers are switching because of price.
- Calculate contribution and likely volume needed to cover the cut.
- Consider capacity, brand position and alternative responses.
The business should estimate price sensitivity and the likely volume gained, then calculate whether the lower contribution per unit can be offset. It should also consider spare capacity and whether a targeted offer, improved service or differentiation is more suitable than a broad price cut.
Look for these in your work
- Demand response is investigated
- Cost or contribution is considered
- An alternative is compared
Common mistakes
- Calling a change in own-price quantity demanded a demand shift
- Assuming every business can raise prices when demand rises
- Ignoring costs, capacity and competitor responses
What can you explain now?
Which is most likely to shift demand for a product?
Compare with the explanation
A change in customer income, with the product's own price unchanged
Income is a non-price determinant of demand.
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Make it stick
Which factors can shift demand, which can shift supply, and why is a business's price response conditional?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.