The Law of Demand
The Law of Demand and the Demand Curve
We begin with demand because demand is usually easier to understand from our personal experiences. We are all consumers and we all demand goods and services. Demand is derived from consumers' tastes and preferences, and it is bound by income. In other words, given a limited income (whether it be $30,000 or $5 million), the consumer must decide what goods and services to purchase. Within his budget, the consumer will purchase those goods and services that he likes best. Each consumer will purchase different things because individual preferences and incomes differ.The law of demand holds that other things equal, as the price of a good or service rises, its quantity demanded falls. The reverse is also true: as the price of a good or service falls, its quantity demanded increases. This law is a simple, common sense principle. Think of your trips to the grocery store. When the price of orange juice rises, for example, you buy less of it. When that item is on sale, you purchase more of it. This is all that we mean by the law of demand.
Table 1 lists the monthly quantity of rental videos demanded by an individual given several different prices. If the rental price is $5, the consumer rents 10 videos per month. If the price falls to $4, the quantity demanded increases to 20 videos, and so on. The figure titled "Demand Curve" plots the inverse relationship between price and quantity demanded.
| TABLE 1 Demand for Videos | |
|---|---|
| Price | Quantity Demanded |
| $5 | 10 |
| $4 | 20 |
| $3 | 30 |
| $2 | 40 |
| $1 | 50 |
A demand curve is a graphical depiction of the law of demand. We plot price on the vertical axis and quantity demanded on the horizontal axis. As the figure illustrates, the demand curve has a negative slope, consistent with the law of demand.
