Law of Demand | Definition, Example, Exceptions, Assumptions

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Tutorial Topic: What is the law of demand, definition, example, meaning, assumptions and exceptions to the law of demand.

What is the Law of Demand?

The law of demand is given as, “If the price of a product falls, its quantity demanded increases and if the price of the commodity rises, its quantity demanded falls, other things remaining constant.”


Law of Demand Example

Take the example of an individual, who needs to purchase soft drinks. In the market, a pack of three soft drinks is priced at 120 and the individual purchases the pack. In the next week, the price of the pack is reduced to 105. This time the individual purchases two packs of soft drinks. In the third week, the price of the pack has risen to 130.

This time the individual does not purchase the pack at all. It is a common observation that consumers purchase a commodity in greater quantities when its price is low and vice versa.

This inverse relationship between the demand and price of a commodity is called the law of demand. The following are some popular definitions of the law of demand given by experts:

Read: What is Economics? Definition, Meaning, Assumption


Law of Demand Definition

Robertson defines the law of demand as Other things being equal, the lower the price at which a thing is offered, the more a man will be prepared to buy it.

Marshall defines the law of demand as The greater the amount to be sold, the smaller must be the price at which it is offered in order that it may find purchasers; or in other words, the amount demanded increases with a fall in price and diminishes with a rise in price.

Ferguson defines the law of demand as Law of Demand, the quantity demanded varies inversely with price.

Read: Types of Demand in Economics


Meaning of Law of Demand

The law of demand represents a functional relationship between the price and quantity demanded of a commodity or service.

The law states that the quantity demanded of a commodity increase with a fall in the price of the commodity and vice versa while other factors like consumers’ preferences, level of income, population size, etc. are constant.

Demand is a dependent variable, while the price is an independent variable. Therefore, demand is a function of price and can be expressed as follows:

D= f (P) Where
D= Demand
P= Price
f = Functional Relationship


Assumptions In The Law of Demand

The law of demand follows the assumption of ceteris paribus, which means that the other factors remain unchanged or constant.

As mentioned earlier, the demand for a commodity or service not only depends on its price but also on several other factors such as price of related goods, income, and consumer tastes and preferences.

In the law of demand, other factors are assumed to remain constant while only the price of the commodity changes.

The law of demand is based on the following assumptions:

  • The income of the consumer remains constant.
  • Consumer tastes and preferences remain constant.
  • Price of related goods remains unchanged.
  • Population size remains constant.
  • Consumer expectations do not change.
  • Credit policies remain unchanged.
  • Income distribution remains constant.
  • Government policies remain unchanged.
  • The commodity is a normal commodity.

The law of demand can be understood with the help of certain concepts, such as demand schedule, demand curve, and demand function.

Read: Business Economics | Definition, Scope, Importance


Exceptions To The Law Of Demand

There are certain exceptions to the law of demand that with a fall in price, the demand also falls and there is an increase in demand with an increase in price.

Definition: Exception to the law of demand refers to conditions where the law of demand is not applicable.

In case of exceptions, the demand curve shows an upward slope and referred to as exceptional demand curve. Figure shows an exceptional demand curve:

Giffen goods

Giffen good is a commodity that is unexpectedly consumed more as its price increases. Thus, it is an exception to the law of demand. In the case of Giffen goods, the income effect dominates over the substitution effect.

After the Irish Famine (1845), the potato crop failed due to plant disease, late blight, which destroys both the leaves and the edible roots, or tubers, of the potato plant. Due to this, the price of potatoes increased tremendously.

Despite the fact that the price increase made people to find substitutes of potatoes, they moved away from luxury products so that their overall consumption of potatoes increased.

Articles of distinction/Veblen goods

Named after economist, Thorstein Veblen, these commodities satisfy the desires of the upper-class people in society. Veblen goods include those commodities whose demand is proportional to their price and thus, they are exceptions to the law of demand.

These articles are purchased only by a few rich people to feel superior to the rest. For example, diamonds, rare paintings, vintage cars, and antique goods are examples of Veblen goods.

Consumers’ ignorance

Consumers’ ignorance is another factor that motivates people to purchase a commodity at a higher price, which violates the law of demand. This results out of the consumers’ biases that a high-priced commodity is better in quality than a low-priced commodity.

Situations of crisis

Crisis such as war and famine negate the law of demand. During crisis, consumers tend to purchase in larger quantities with the purpose of stocking, which further accentuates the prices of commodities in the market. They fear that goods would not be available in the future.

On the other hand, at the time of depression, a fall in the price of commodities does not induce consumers to demand more.

Future price expectations

When consumers expect a rise in the prices of commodities, they tend to purchase commodities at existing high prices. For example, speculation of market strategists on an increase in gold prices in the future induces consumers to purchase higher quantities in order to stock gold.

On the contrary, if consumers expect a fall in the price of a commodity, they postpone the purchase for the future.

Read: Demand Schedule | Definition, Example, [Individual & Market]


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