Microeconomics: Theory and Applications with Calculus, 4e

2.1 Demand

The quantity demanded is the amount of a good that consumers are willing to buy at a given price during a specified period (such as a day or a year), holding constant the other factors that influence purchases. The quantity demanded of a good or service can exceed the quantity actually sold. For example, as a promotion, a local store might sell Blu-ray Discs for $1 each today only. At that low price, you might want to buy 10 Blu-ray Discs, but because the store has only 5 remaining, you can buy at most 5 Blu-ray Discs. The quantity you demand is 10 Blu-ray Discs—it’s the amount you want—even though the amount you actually buy is 5.

Potential consumers decide how much of a good or service to buy based on its price, which is expressed ...