How does income change demand for a product?
Income elasticity of demand measures the percentage response of quantity demanded when consumer income changes.
Mechanism and examples
A positive coefficient may indicate a normal good and a negative one an inferior good. A value above one means demand grows faster than income. Classification depends on the product, population and income range studied. Analysis should state the assumption that other conditions remain unchanged, because simultaneous changes in real data can alter the outcome. In practice, it first identifies the decision makers, the price or quantity that changes, and the time horizon over which the response is measured. This explains why the same concept can produce different outcomes for households, firms and whole economies.
What matters when interpreting it?
A product may appear necessary for one income group and discretionary for another. When prices and preferences also change, the income effect must be separated. The coefficient does not measure social value or importance of need. Data sources, periods, price adjustments and comparison groups can affect the result. To understand why an indicator changed, it is checked against related production, income, employment or price evidence. The concept should therefore be used as an analytical comparison tool with visible assumptions, not as a certain forecast or personal financial recommendation on its own.