Consider what might happen if you lose your job. If you aren’t earning money, you aren’t likely to buy many CDs or movie tickets or magazines - no matter how low the price. Similarly, when national unemployment rises, people who are out of work are more likely to spend their limited funds on food and housing than on entertainment.
Fewer people would be buying DVDs at every price, so market demand would drop. This is an example of a change in demand, which occurs when a change in the marketplace such as high unemployment prompts consumers to buy different amounts of a good or service at every price. Change in demand is also called a shift in demand because it actually shifts the position of the demand curve.
Six factors can cause a change in demand: income, market size, consumer tastes, consumer expectations, substitute goods, and complementary goods. An explanation of each one follows.