2.1.1—Law of demand

The law of demand states that, ceteris paribus, a higher price causes a lower quantity demanded and a lower price causes a higher quantity demanded over a stated period.

This Objective establishes the observable inverse relationship while holding income, tastes, related-good prices, expectations and consumer numbers constant. The deeper income, substitution and marginal-utility explanations belong to HL 2.1.2.

Identify the good's own price change, explicitly hold non-price determinants constant, and predict the opposite change in quantity demanded.

If coffee rises from $3 to$4 per cup while other conditions are unchanged, quantity demanded falls—for example from 120 to 90 cups per day.

Demand is the whole relationship; quantity demanded is one amount at one price. The law is ceteris paribus, not a claim that every observed sales change comes only from price.