Revise Elasticity for Cambridge 9609 (8.1.1)

Price Elasticity of Demand (PED) measures the responsiveness of quantity demanded to a change in a product's own price. The formula is: Percentage Change in Quantity Demanded ÷ Percentage Change in Price. The result indicates how sensitive consumers are to price adjustments. If the absolute value is greater than 1, demand is 'price elastic', meaning a small price change causes a large change in demand. If it is less than 1, demand is 'price inelastic', meaning demand is largely unresponsive to price changes. A value of 1 is 'unitary elastic'. This concept is fundamental for pricing strategy; for an inelastic good, a price rise increases total revenue, whereas for an elastic good, a price cut is needed to increase total revenue.

Several factors determine a product's PED. The most important is the availability of substitutes; the more close substitutes there are, the more elastic the demand. Secondly, the nature of the good matters: necessities, such as bread or petrol, tend to have inelastic demand, while luxuries, like foreign holidays, have elastic demand. The proportion of income a product takes up is also key; expensive items like cars are price elastic as a price change has a significant impact on a consumer's budget. Finally, time plays a role. In the short term, demand is often inelastic as consumers have little time to change habits, but over the long term, demand becomes more elastic as they can find alternatives.

Income Elasticity of Demand (YED) measures how the quantity demanded of a product responds to a change in consumer incomes. The formula is: Percentage Change in Quantity Demanded ÷ Percentage Change in Income. Unlike PED, the sign of the YED value is crucial. A positive YED indicates a 'normal good', where demand rises as incomes rise. A negative YED signifies an 'inferior good', where demand falls as incomes rise (e.g., consumers switch from budget brands to premium brands). Normal goods can be further classified: if YED is between 0 and 1, it is an income-inelastic necessity; if YED is greater than 1, it is an income-elastic luxury. Businesses use YED to forecast demand during different phases of the economic cycle.

Cross Elasticity of Demand (XED) measures the responsiveness of demand for one product (Good A) following a price change of another product (Good B). The formula is: % Change in Quantity Demanded of Good A ÷ % Change in Price of Good B. The sign of the XED value defines the relationship between the two products. A positive XED indicates they are 'substitutes' – a price rise for Good B leads to a rise in demand for Good A. A negative XED indicates they are 'complements' – a price rise for Good B leads to a fall in demand for Good A as well. A value close to zero suggests the goods are unrelated. Businesses use XED to understand their competitive environment and identify opportunities for complementary product strategies.

A manager uses all three elasticity measures for comprehensive strategic planning. PED is used to set the optimal price for a product to achieve revenue objectives. YED is crucial for forecasting and managing the product portfolio; a business might want a mix of normal and inferior goods to maintain sales during both economic booms and recessions. XED informs competitive strategy, helping a business anticipate the impact of a rival's price cut and decide how to react. For example, a high positive XED with a competitor's product signals a significant threat. Using these concepts together allows for more robust decisions on pricing, production levels, and marketing focus, creating a dynamic response to changing market conditions.

PED = % Δ Qd ÷ % Δ P

YED = % Δ Qd ÷ % Δ income

XED = % Δ Qd of good A ÷ % Δ P of good B