How sharply do buyers and sellers react to a change in price or income, and why does it matter?
Elasticity: price elasticity of demand and its calculation and determinants, the link to total revenue, and price elasticity of supply, income elasticity and cross elasticity.
An SQA Higher Economics answer on elasticity, covering how to calculate price elasticity of demand and interpret it, the factors that make demand elastic or inelastic, the link between PED and total revenue, and price elasticity of supply, income elasticity and cross elasticity of demand.
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What this key area is asking
The SQA wants you to measure and interpret price elasticity of demand (PED): calculate it, classify demand as elastic, inelastic or unit elastic, explain what makes it so, and link it to total revenue. You should also know price elasticity of supply (PES), income elasticity of demand (YED) and cross elasticity of demand (XED). Data-response questions reward a correct calculation followed by a clear interpretation, so always do both.
Price elasticity of demand: calculation and classification
Classify the result:
- Elastic (PED greater than 1): quantity demanded changes proportionately more than price. The demand curve is relatively flat.
- Inelastic (PED less than 1): quantity demanded changes proportionately less than price. The curve is relatively steep.
- Unit elastic (PED = 1): quantity and price change in the same proportion.
- Two extremes complete the set: perfectly inelastic (PED = 0, a vertical curve) and perfectly elastic (PED = infinity, a horizontal curve).
What makes demand elastic or inelastic
These factors explain real patterns: petrol and cigarettes are price inelastic (few close substitutes, habitual or necessary), which is one reason governments tax them; foreign holidays are price elastic (many substitutes and a large share of income).
Elasticity and total revenue
The most useful application links PED to a firm's total revenue (price multiplied by quantity sold).
- If demand is elastic, a price cut raises total revenue (the proportionately larger rise in quantity outweighs the lower price), and a price rise reduces it.
- If demand is inelastic, a price rise raises total revenue (the small fall in quantity is outweighed by the higher price), and a price cut reduces it.
- If demand is unit elastic, total revenue is unchanged by a price change.
The other elasticities
Higher asks you to recognise three further measures:
- Price elasticity of supply (PES) = % change in quantity supplied divided by % change in price. Supply is more elastic when firms have spare capacity, can store stock, or have time to adjust; primary goods such as crops are often inelastic in the short run.
- Income elasticity of demand (YED) = % change in quantity demanded divided by % change in income. It is positive for normal goods, negative for inferior goods, and greater than 1 for luxuries (income elastic).
- Cross elasticity of demand (XED) = % change in quantity demanded of good A divided by % change in the price of good B. It is positive for substitutes and negative for complements.
Worked example: a calculation and its meaning
Why elasticity matters
Elasticity turns the direction of a price change into a size, which is what firms and governments actually need. Pricing decisions, the revenue from indirect taxes, the burden of a tax between producer and consumer, and the design of subsidies all depend on elasticities. It is the bridge between the simple demand and supply curves and real commercial and policy choices.
Try this
Q1. Demand for a product is price inelastic. A firm cuts its price. State and explain what happens to total revenue. [2 marks]
- Cue. Revenue falls; with inelastic demand the rise in quantity is proportionately smaller than the fall in price, so price times quantity falls.
Q2. The cross elasticity of demand between two goods is +1.8. Explain what this tells you about the relationship between the goods. [2 marks]
- Cue. A positive XED means the goods are substitutes; the large value (greater than 1) means they are close substitutes, so a rise in the price of one causes a large rise in demand for the other.
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA Higher (style)4 marksA firm raises its price by 10% and finds quantity demanded falls by 25%. Calculate the price elasticity of demand and explain what it shows.Show worked answer →
Worth 4 marks. The calculation earns marks; the interpretation must follow.
Calculation (about 2 marks). Price elasticity of demand . Quoting the value (ignoring the sign) is acceptable.
Interpretation (about 2 marks). Because the figure is greater than 1 (in absolute terms), demand is price elastic: quantity demanded changes proportionately more than price. A 1% price rise cuts demand by 2.5%. For this firm, raising price has reduced total revenue, because the large fall in quantity outweighs the higher price per unit.
SQA Higher (style)6 marksExplain why the price elasticity of demand for a good is useful to a business deciding whether to raise its price.Show worked answer →
Worth 6 marks. Link elasticity to total revenue with reasoning for both cases.
Elastic demand (about 3 marks). If demand is price elastic (PED greater than 1), a price rise causes a proportionately larger fall in quantity demanded, so total revenue falls. A business facing elastic demand, perhaps because there are close substitutes, should be cautious about raising price and might instead cut price to raise revenue.
Inelastic demand (about 3 marks). If demand is price inelastic (PED less than 1), a price rise causes a proportionately smaller fall in quantity, so total revenue rises. A business selling a good with few substitutes or one seen as a necessity can raise price and increase revenue. Knowing the PED therefore tells the firm the likely effect of a price change on its revenue, which is why it is commercially important.
Related dot points
- The theory of demand: the law of demand, the demand curve, the difference between a movement along and a shift of the curve, and the non-price determinants of demand.
An SQA Higher Economics answer on the theory of demand, covering the law of demand and why the demand curve slopes down, the crucial difference between a movement along the curve and a shift of it, and the non-price determinants of demand such as income, the prices of substitutes and complements, tastes and expectations.
- The theory of supply: the law of supply, the supply curve, the difference between a movement along and a shift of the curve, and the non-price determinants of supply.
An SQA Higher Economics answer on the theory of supply, covering the law of supply and why the supply curve slopes up, the difference between a movement along the curve and a shift, and the non-price determinants of supply such as costs of production, technology, taxes and subsidies, and the price of other goods.
- Production and costs: production and productivity, fixed and variable costs, total, average and marginal cost, revenue and profit, and economies and diseconomies of scale.
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An SQA Higher Economics answer on price determination, covering market equilibrium where demand and supply meet, surpluses and shortages, how shifts in demand or supply change the equilibrium price and quantity, and the rationing, signalling and incentive functions of the price mechanism.
Sources & how we know this
- Higher Economics Course Specification — SQA (Qualifications Scotland) (2024)