A decrease in the preference or taste for a good will shift the demand curve for the good to the left. Prices of Substitutes and Complements. Substitutes are goods that can replace each other in consumption. They are related such that an increase in the price of one good will cause an increase in the demand for the other good. Examples of substitutes include butter and margarine and coffee and tea.
Complements are goods that are jointly consumed.
They are related such that an increase in the price of one good will cause an decrease in the demand for the other good. Examples of complements include lamps and light bulbs and milk and cereal. Expectations About the Future. Expectations about future income and prices can shift the demand curve. For example, someone who expects higher income or prices in the future will probably buy more goods today.