What does income elasticity of demand primarily measure?

Income elasticity of demand primarily measures how the quantity demanded of a good responds to changes in consumer income. When income elasticity is calculated, it provides insight into whether a good is a luxury or a necessity. A positive income elasticity indicates that as income increases, the demand for the good also increases, suggesting that it is a normal good. Conversely, a negative income elasticity suggests that the good is an inferior good, meaning that as income rises, the demand for it decreases. Understanding this relationship is crucial for businesses and economists, as it aids in predicting consumer behavior and making informed production and marketing decisions. Thus, the correct choice directly reflects the definition and significance of income elasticity in economic analysis.