Basis     of Difference      Contraction of Demand     Decrease in Demand   Meaning When quantity demand for a commodity falls due to rise in the price, keeping other factors as constant is called a contraction of demand. When demand for a commodity decreases due to change in other factors, keeping price as constant is called a decrease in demand. Cause Rise in price of the commodity Several causes: a. Decrease in price of the substitute goods b. Increase in price of the complementary goods c. Decrease in income in case of normal goods. d. Unfavorable tastes and preferences are developed. Effect on demand curve It is shown as movement from right to left on the same demand curve. It is shown as a backward or leftward  shift  in the demand curve. Concept It is a quantity demand concept