Slope of the Demand Curve:

Demand Curve is Negatively Sloped:

The demand curve generally slopes downward from left to right. !t has a negative slope because the two important variables price and quantity work in opposite direction. As the price of a commodity decreases, the quantity demanded increases over a specified period of time. and vice versa, other , things remaining constant. The fundamental reasons for demand curve to

slope downward are as follows:

(i) Law of diminishing marginal utility: The law of demand is based on the law of diminishing marginal utility. According to the cardinal utility approach, when a consumer purchases more units of a commodity, its marginal utility declines. The consumer, therefore, will purchase more units of that commodity only if its price falls. Thus. a decrease in price brings about an increase, in demand. The demand curve, therefore, is downward sloping.

(ii) Income effect: Other things being equal, when the price of a commodity decreases, the real income or the purchasing power of the household increases. The consumer is now in a position to purchase more commodities with the same income. The demand for a commodity thus increases not only from the existing buyers but also from the new buyers who were earlier unable to purchase at higher price. When at a lower price, there is a greater demand for a commodity by the households, the

demand curve is bound to slope downward from left to right.

(iii) Substitution effect: The demand curve slopes downward from left to right also because of the substitution effect. For instance, the price of meat falls and the prices of other substitutes say poultry and beef remain constant. Then the households would prefer to purchase meat because it is now relatively cheaper. The increase in demand with a fall in the price of meat will move the demand curve downward from left to right.

(iv) Entry of new buyers: When the price of a commodity falls, its demand not only increases from the old buyers but the new buyers also enter the market. The combined result of the income and substitution effect is that demand extends, ceteris paribus, as the .price falls. The demand curve slopes downward from left to right.

Exception to the Law of Demand:

There is no doubt that 'typical demand curve has a tendency to fall downward from left to right But sometimes it can also happen that the demand curve may slope upward from left to right. In other words, it may have a positively inclined curve. For instance, if people expect the price to go- up in the near future, they will purchase more commodities at a higher price. Similarly, some of the articles of ostentation have a greater demand when their price rises and lesser demand when price falls. For instance, diamonds'

may have a large buyers when its price is $50 than at $1. Sometimes, people in ignorance may also purchase more commodities at a higher price. The upward sloping demand curve is shown in the diagram below:

In the Fig. (4.5) we assume that conditions in demand have changed due to exceptions and the households demand for prestigious goods has increased, with the rise in prices. When the price of a diamond is $2, the demand is 20 units. When the price rises to $5, the demand increases to 40 units.