Sun Apr 14 Determinants of Demand There are at least Six factors that can cause a change in demand: income, market size, consumer tastes, consumer expectations, substitute goods, and complementary goods. An explanation of each one follows. FACTOR 1 Income If a consumer's income changes, either higher or lower, that person's ability to buy goods and services also changes. For example, Tyler works at a garden center. He uses his earnings to buy baseball cards for his collection. In the fall, people garden less and buy fewer gardening products, so Tyler works fewer hours. His smaller paycheck means that he has less money to spend, so he demands fewer baseball cards at every price. Figure 4.8 shows this change. The entire demand curve shifts to the left. 1. Explain the effect of income on demand