Read this section to learn about the theory of demand. Attempt the "Try It" problem. Use the data from the text to practice constructing and drawing the demand curve on your own, either on a paper or in Excel. Take a moment to read through the stated learning outcomes for this chapter of the text, which you can find at the beginning of each section.

Changes in Demand


As incomes rise, people increase their consumption of many goods and services, and as incomes fall, their consumption of these goods and services falls. For example, an increase in income is likely to raise the demand for gasoline, ski trips, new cars, and jewelry. There are, however, goods and services for which consumption falls as income rises ­– and rises as income falls. As incomes rise, for example, people tend to consume more fresh fruit but less canned fruit.

A good for which demand increases when income increases is called a normal good. A good for which demand decreases when income increases is called an inferior good. An increase in income shifts the demand curve for fresh fruit (a normal good) to the right; it shifts the demand curve for canned fruit (an inferior good) to the left.