When the price of commodity falls, the consumer can purchase the commodity in excess quantity with his/her income. Or, if he buys a commodity like before, some money will be left with him because he has to spend less due to lower cost. In other words, the actual income or purchasing power of the consumer increases as a result of the fall in the price of a commodity. This increase in real income inspires the consumer to buy more of that commodity. It is called the Income Effect of the Change in the price of the commodity.
