Explain the causes of a leftward shift in demand curve of a commodity?

Main causes of decrease in demand or leftward shift in demand curve of a commodity are as under:

(i) Income of the Consumer: With decrease in income of the consumer, the demand curve for normal goods shifts to the left.

(ii) Price of Related Goods: In case of substitute goods, demand for a commodity falls (and demand curve shifts to the left) with fall in price of the substitute commodity. In case of complementary goods, demand for the commodity falls with a rise in the price of complementary commodity.

(iii) Tastes and Preferences: If consumer's tastes and preferences change against the commodity, the quantity demanded of the commodity falls (implying a shift in demand curve to the left).

(iv) Expectations: If the consumer expects that price in the near future will fall, he will but, less quantity at the prevailing price and hence demand curve shifts to the left.