Final answer:
The ratio of the percentage change in quantity demanded to the percentage change in price describes the price elasticity of demand, which indicates how responsive the quantity demanded is to price changes. This is distinct from income and cross-price elasticities of demand.
Step-by-step explanation:
The ratio of the percentage change in quantity demanded to the percentage change in price is referred to as the price elasticity of demand. This economic concept reflects the responsiveness of the quantity demanded of a good or service to a change in its price. For instance, if the price of a product increases by 10% and the quantity demanded decreases by 20%, the price elasticity of demand would be -2.0, indicating an elastic demand. In this scenario, the quantity demanded is highly responsive to changes in price. It's essential to differentiate price elasticity from income elasticity of demand, which measures the change in quantity demanded in response to a change in income, or cross-price elasticity of demand, which measures the change in quantity demanded of one good in response to a price change in another good.