D) The factors influencing income elasticity of demand

The idea

The income elasticity of demand (YED) is influenced by several factors, primarily the nature of the good and consumer perceptions. Whether a good is viewed as a necessity or a luxury dictates its YED; basic foodstuffs typically have a low, positive YED because they are bought regardless of income fluctuations, whereas designer clothing has a high, positive YED. The current income level of consumers also matters; a good might be a luxury at lower income levels but become a necessity or an inferior good as incomes rise. Furthermore, the availability of higher-quality substitutes influences YED; if incomes rise and better alternatives exist, consumers will abandon the original product, rendering it an inferior good with a negative YED.

What earns the marks

• Identifies the degree of necessity as a primary determinant of YED.
• Explains how consumer income levels affect whether a good is perceived as normal or inferior.
• Recognises that the availability of superior substitutes can turn a normal good into an inferior good as incomes rise.
• Evaluates how changes in societal trends or branding can shift a product from a necessity to a luxury.

Common mistakes and how to put them right

• Confusing factors affecting YED with those affecting PED.

  Put it right: Factors like the proportion of income spent or time period primarily affect PED, whereas YED is driven by the good's status as a necessity, luxury, or inferior item.

• Assuming a good's YED is static for all consumers.

  Put it right: A good can be a normal good for a low-income earner but an inferior good for a high-income earner.

• Believing that all goods become luxuries as income falls.

  Put it right: Necessities often remain necessities with a YED between 0 and 1, regardless of minor income drops, because they are essential for survival.

Exam tips

• When evaluating YED, always consider the context of the target market's current income level.
• Use examples, such as public transport versus private car ownership, to illustrate how a good can transition from normal to inferior.
• Read multiple-choice scenarios carefully to determine if a shift in consumer perception has altered the good's YED classification.