Demand schedule

The demand schedule, depicted graphically as the demand curve, represents the amount of some good that buyers are willing and able to purchase at various prices, assuming all determinants of demand other than the price of the good in question, such as income, tastes and preferences, the price of substitute goods, and the price of complementary goods, remain the same. Following the law of demand, the demand curve is almost always represented as downward-sloping, meaning that as price decreases, consumers will buy more of the good.^[2]

Just as the supply curves reflect marginal cost curves, demand curves are determined by marginal utility curves.^[3] Consumers will be willing to buy a given quantity of a good, at a given price, if the marginal utility of additional consumption is equal to the opportunity cost determined by the price, that is, the marginal utility of alternative consumption choices. The demand schedule is defined as the willingness and ability of a consumer to purchase a given product in a given frame of time.

As described above, the demand curve is generally downward-sloping. There may be rare examples of goods that have upward-sloping demand curves. Two different hypothetical types of goods with upward-sloping demand curves are Giffen goods (an inferior but staple good) and Veblen goods (goods made more fashionable by a higher price).

By its very nature, conceptualizing a demand curve requires that the purchaser be a perfect competitor—that is, that the purchaser has no influence over the market price. This is because each point on the demand curve is the answer to the question "If this buyer is faced with this potential price, how much of the product will it purchase?" If a buyer has market power, so its decision of how much to buy influences the market price, then the buyer is not "faced with" any price, and the question is meaningless.

As with supply curves, economists distinguish between the demand curve of an individual and the market demand curve. The market demand curve is obtained by summing the quantities demanded by all consumers at each potential price. Thus in the graph of the demand curve, individuals' demand curves are added horizontally to obtain the market demand curve.

The determinants of demand follow:

1. Income

2. Tastes and preferences

3. Prices of related goods and services

4. Expectations

5. Number of Buyers