Here are some revision notes on YED which might useful for the CIE AS Economics exam next month. Quite a few of the class had never come across this graph which is popular in multiple-choice questions. It is important that you read the axis.
Usefulness of Income Elasticity of Demand
Knowledge of income elasticity of demand for different products helps firms predict the effect of a business cycle on sales. All countries experience a business cycle where actual GDP moves up and down in a regular pattern causing booms and slowdowns or perhaps a recession. The business cycle means incomes rise and fall.
Luxury products with high income elasticity see greater sales volatility over the business cycle than necessities where demand from consumers is less sensitive to changes in the economic cycle
The NZ economy has enjoyed a period of economic growth over the last few years. So average real incomes have increased, but because of differences in income elasticity of demand, consumer demand for products will have varied greatly over this period.
Over time we expect to see our real incomes rise. And as we become better off, we can afford to increase our spending on different goods and services. Clearly what is happening to the relative prices of these products will play a key role in shaping our consumption decisions. But the income elasticity of demand will also affect the pattern of demand over time. For normal luxury goods, whose income elasticity of demand exceeds +1, as incomes rise, the proportion of a consumer’s income spent on that product will go up. For normal necessities (income elasticity of demand is positive but less than 1) and for inferior goods (where the income elasticity of demand is negative) – then as income rises, the share or proportion of their budget on these products will fall. See table below for a summary of values.