Consumer Demand - Demand Curve, Demand Function & Law of Demand
What is Demand?
Demand for a commodity refers to the quantity of the commodity that people are willing to purchase at a specific price per unit of time, other factors (such as price of related goods, income, tastes and preferences, advertising, etc) being constant.
Demand includes the desire to buy the commodity accompanied by the willingness to buy it and sufficient purchasing power to purchase it. For instance-Everyone might have willingness to buy Mercedes-S class but only a few have the ability to pay for it. Thus, everyone cannot be said to have a demand for the car Mercedes-s Class.
Demand may arise from individuals, household and market. When goods are demanded by individuals (for instance-clothes, shoes), it is called as individual demand. Goods demanded by household constitute household demand (for instance-demand for house, washing machine). Demand for a commodity by all individuals/households in the market in total constitute market demand.
Demand Function
Demand function is a mathematical function showing relationship between the quantity demanded of a commodity and the factors influencing demand.
In the above equation,
Dx = Quantity demanded of a commodity
Px = Price of the commodity
Py = Price of related goods
T = Tastes and preferences of consumer
Y = Income level
A = Advertising and promotional activities
Pp = Population (Size of the market)
Ep = Consumers expectations about future prices
U = Specific factors affecting demand for a commodity such as seasonal changes, taxation policy, availability of credit facilities, etc.
Law of Demand
The law of demand states that there is an inverse relationship between quantity demanded of a commodity and its price, other factors being constant. In other words, higher the price, lower the demand and vice versa, other things remaining constant.
Demand Schedule
Demand schedule is a tabular representation of the quantity demanded of a commodity at various prices. For instance, there are four buyers of apples in the market, namely A, B, C and D.
PRICE (Rs. per dozen) | Buyer A (demand in dozen) | Buyer B (demand in dozen) | Buyer C (demand in dozen) | Buyer D (demand in dozen) | Market Demand (dozens) |
10 | 1 | 0 | 3 | 0 | 4 |
9 | 3 | 1 | 6 | 4 | 14 |
8 | 7 | 2 | 9 | 7 | 25 |
7 | 11 | 4 | 12 | 10 | 37 |
6 | 13 | 6 | 14 | 12 | 45 |
The demand by Buyers A, B, C and D are individual demands. Total demand by the four buyers is market demand. Therefore, the total market demand is derived by summing up the quantity demanded of a commodity by all buyers at each price.
Demand Curve
Demand curve is a diagrammatic representation of demand schedule. It is a graphical representation of price- quantity relationship. Individual demand curve shows the highest price which an individual is willing to pay for different quantities of the commodity. While, each point on the market demand curve depicts the maximum quantity of the commodity which all consumers taken together would be willing to buy at each level of price, under given demand conditions.

Demand curve has a negative slope, i.e, it slopes downwards from left to right depicting that with increase in price, quantity demanded falls and vice versa. The reasons for a downward sloping demand curve can be explained as follows-
Exceptions to Law of Demand
The instances where law of demand is not applicable are as follows-
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