Demand is defined as the entire demand for a product or a service. A demand curve is a graphical diagram that illustrates the relationship between the price of different commodities or services and the amount that will be purchased. Ordinarily the demand curve slopes downwards, that is from left to right. The downward slope of the demand curve depicts that as the price of the commodities increase, the consumers will demand less of that product or service. On the other hand, if the price of commodities declines the consumers will demand more of that product.
There is a difference that exists between changes in demand and changes in the quantity demanded. A change in demand is depicted by shifts in the demand curve. According to John et al, the shift may either be to the right or left of the demand curve. Changes in demand are a result of various factors such as the consumer’s level of income, and changes in the tastes and preferences of the consumers. For instance, if there is a change in fashion for a particular commodity, less of that commodity will be demanded. This will cause the demand for that commodity to shift to the left depicting a change in demand.
Quantity demanded refers to the amount that an individual will buy at a given market price. The quantity demanded of a particular product or service changes from time to time. This change in quantity demanded is depicted by movements along the demand curve. The movement along the curve is caused by changes in price. For instance; if the price of a commodity declines while the other factors affecting demand remain constant, the consumers will be able to buy more of that commodity. This shows that there is a change in the quantity demanded.