# The demand curve and its inverse relationship between price quantity demanded

### Law of demand (article) | The demand curve | Khan Academy The inverse relationship between price of a commodity and its quantity demanded is explained by law of That is why, demand curve is downward sloping. In economics, the demand curve is the graph depicting the relationship between the price of a certain commodity and the amount of The standard form of the demand equation can be converted to the inverse There is movement along a demand curve when a change in price causes the quantity demanded to change. Economists call this inverse relationship between price and quantity demanded the law of demand. The law of demand assumes that all other variables that.

As a result of this shift, the quantity demanded at all prices will have changed. Reasons for a change in demand.

It is important to keep straight the difference between a change in quantity demanded, or a movement along the demand curve, and a change in demand, or shift in the demand curve. There is only one reason for a change in the quantity demanded of good X: Changes in the price of related goods: The demand for good X may be changed by increases or decreases in the prices of other, related goods. These related goods are usually divided into two categories called substitutes and complements. A substitute for good X is any good Y that satisfies most of the same needs as good X. For example, if good X is butter, a substitute good Y might be margarine. When two goods X and Y are substitutes, then as the price of the substitute good Y rises, the demand for good X increases and the demand curve for good X shifts to the right, as in Figure b. Conversely, as the price of the substitute good Y falls, the demand for good X decreases and the demand curve for good X shifts to the left, as in Figure a.

A complement to good X is any good that is consumed in some proportion to good X. For example, if good X is a pair of shoelaces, then a complement good Y might be a pair of shoes. When two goods X and Y are complements, then as the price of the complementary good Y rises, the demand for good X decreases and the demand curve for good X shifts to the left, as in Figure a. Furthermore, researchers found that the success of the law of demand extends to animals such as rats, under laboratory settings.

## Demand curve

In some cases, however, this may not be true. There are certain goods which do not follow this law. These include [[Veblen goods] [Giffen goods] and expectations of future price changes. Further exception and details are given in the sections below.

## Law of demand

Giffen goods[ edit ] Initially proposed by [Sir Robert Giffen], economists disagree on the existence of Giffen goods in the market. A Giffen good describes an inferior good that as the price increases, demand for the product increases. As an example, during the Irish Potato Famine of the 19th century, potatoes were considered a Giffen good.

Potatoes were the largest staple in the Irish diet, so as the price rose it had a large impact on income. Price elasticity of demand PED [ edit ] Main article: Price elasticity of demand PED is a measure of the sensitivity of the quantity variable, Q, to changes in the price variable, P.

PED is negative because of the inverse relationship between the price of a good and the quantity of the good demanded, a consequence of the law of demand. The elasticity of demand indicates how sensitive the demand for a good is to a price change.

### Demand curve - Wikipedia

If the absolute value of PED is between zero and 1, demand is said to be inelastic; if the absolute value of PED equals 1, the demand is unitary elastic; and if the absolute value of Price elasticity of demand is greater than 1, demand is elastic.

A low coefficient implies that changes in price have little influence on demand. A high elasticity indicates that consumers will respond to a price rise by buying a lot less of the good and that consumers will respond to a price cut by buying a lot more Taxes and subsidies[ edit ] A sales tax on the commodity does not directly change the demand curve, if the price axis in the graph represents the price including tax. Similarly, a subsidy on the commodity does not directly change the demand curve, if the price axis in the graph represents the price after deduction of the subsidy.