## Elasticity of Demand – CBSE Notes for Class 12 Micro Economics

Introduction

This is a numerical based chapter on elasticity of demand, price elasticity of demand and its measurements, also discussing the factors affecting it.

1. Elasticity of Demand: The degree of responsiveness of demand to the changes in determinants of demand (Price of the commodity, Income of a Consumer, Price of related commodity) is known as elasticity of Demand.
2. It may be of three types: namely,
(a) Price elasticity of Demand.
(b) Income elasticity of Demand,
(c) Cross elasticity of Demand. 3. (a) The degree of responsiveness of quantity demanded to changes in price of commodity is known as price elasticity of Demand.
(b) It is quantitative statement, i.e., it tells us the magnitude of the change in quantity demanded as a result of change in price.
4. The degree of responsiveness of demand to change in income of consumer is known as income elasticity of demand.
5. The degree of responsiveness of demand to change in the price of related goods (substitute goods, complementary goods) is known as cross elasticity of demand.
Note: Income and cross elasticity of demand is outside the scope of 12 class syllabus. So, this chapter deal with price elasticity of demand.
6. Percentage Method/Flux Method for calculating price elasticity of demand:
According to this method, price elasticity of demand is measured by dividing the percentage change in quantity demand by the percentage change in price. Note: Mathematically speaking, price elasticity of demand (ep) is negative, since the change in quantity demanded is in opposite direction to the change in price. When price falls, quantity demanded rises and vice-versa. But for the sake of convenience in understanding the magnitude of response of quantity demanded to the change in price, we ignore the negative sign and take into account only the numerical value of the elasticity. Thus, if 5% change in price leads to 15% change in quantity demanded of good X and 30% change in that of Y, the above formula of elasticity will give the value of price elasticity of good X equal to 3 and of good Y equal to 6. It indicates that the quantity demanded of good Y changes much more than that of good X in response to a given change in price. But if we write minus signs before the numerical values of elasticities of two goods, that is, if we write the elasticities as – 3 and – 6 respectively as strict mathematics would require us to do, then since – 6 is smaller than – 3, we would be misled in concluding that price elasticity of demand of Y is less than that of X.
But as we have noted above, response of demand for Y to the change in price is greater than that of X, it is better to ignore minus signs and draw conclusions from
the numerical values of elasticities. Hence by convention minus sign before the value of price elasticity of demand is generally ignored in economics.
7. There are five degrees of price elasticity of demand.
(a) Unitary elastic demand: If percentage change in the quantity demanded is equal to percentage change in price of the commodity, then ED = 1 and the result is known as unitary elastic demand.   Negative sign indicates the inverse relationship between price and the quantity demanded.
PED = 1 [Unitary elastic demand]
(b) More than unitary elastic demand or elastic demand: If percentage change in quantity demanded is more than the percentage change in price of the commodity then, ED > 1 and result is known as more than unit elastic demand. (c) Less than unitary elastic demand or inelastic demand: If percentage change in quantity demanded is less than the percentage change in price of the commodity, then ED < 1 and the result is known as less than unit elastic demand. (d) Perfectly elastic demand: If quantity demand changes and price remains constant, then ED = Î±  and the result is known as perfectly elastic demand.   (e) Perfectly Inelastic demand: If price is changed ,and quantity demanded constant,then ED=0 and the result is known as Perfectly Inelastic demand. 8. Total outlay method or Total Revenue Method or Expenditure method for calculating price elasticity of demand
(a) Total expenditure method indicates the direction in which total expenditure on a product changes as a result of change in price of the commodity.
(b) According to this method, there are three broad possibilities as shown below:
Case I: Inelastic Demand:
(i) When the total expenditure (Total revenue) varies directly with price, price elasticity of demand is less than one (i.e., demand is inelastic).
(ii) In other words, with the fall in price, total expenditure (Total revenue) decreases or with a rise in price, total expenditure (Total revenue) increases. Case II: Elastic Demand:
(i) When the total expenditure (Total revenue) varies inversely with price, price elasticity of demand is greater than one, (i.e. demand is elastic).
(ii) In other words, with the fall in price, total expenditure (Total revenue) increases, or with a rise in price, total expenditure (Total revenue) decreases. Case III: Unitary Price Elasticity:
(i) When the total expenditure (Total revenue) remains the same, whatever may be the change in the price level, price elasticity of demand is said to be unity. 9. Geometrical Method or Point Method for Calculating Price Elasticity of Demand:
(a) According to point method, elasticity of demand at any point is measured by dividing the lower segment of demand curve with the upper segment of the demand curve at that point. It can be calculated by dividing the lower segment by upper segment. Factors Determining Price Elasticity Of Demand For A Good

They are as follows:
1. Nature of commodity: Elasticity of demand of a commodity is influenced by its nature.
(a) The demand for necessities of life (commodities satisfying minimum basic needs) is less elastic. They are required for human survival and they have to be purchased
whatever may be the price. Therefore, demand for necessities of life does not fluctuate much with price changes.
(b) Whereas, demand for luxury goods is more elastic than the demand for necessities. When the price of luxuries falls, consumers buy more of them and when the prices rises, demand contracts substantially.
Please remember the term “luxury”is a relative term, as a luxury for a low-income
earning worker may be a necessity for rich employer.
2. Availability of substitutes/Substitute goods:
(a) If close substitutes for the commodity are available, the demand for the commodity will be elastic. The reason is that even a small rise in its prices will induce the buyers to go for its substitutes. For example, Pepsi and Coke are considered fairly close substitutes. If the price of coke increases, Pepsi becomes relatively cheaper. Consumer will buy more of Pepsi and less of relatively expensive Coke.
(b) However, the demand for a commodity (such as salt) having no close substitutes is inelastic.
3. Income Level:
(a) Higher income level groups have less elasticity of demand for any commodity as compared to the people with low incomes. It happens because rich people are not influenced much by changes in the price of goods.
(b) But, poor people are highly affected by increase or decrease in the price of goods. As the result of, demand for lower income group is highly elastic.
4. Level of price/Own price of a good:
(a) Higher own price of a good or Costly goods like car, gold etc. have highly elastic demand as their demand is very sensitive to changes in their prices.
(b) However, demand for inexpensive goods like thread, needle etc. is inelastic as change in prices of such goods do not change their demand by a considerable amount.
5. Postponement of Consumption:
(a) Commodities like ice cream, soft drinks, etc. whose demand is not urgent, have highly elastic demand as their consumption can be postponed in case of an increase in their prices.
(b) However, commodities with urgent demand like life saving drugs, have inelastic demand because of their immediate requirement.
6. Number of Uses:
(a) If the commodity under consideration has many alternative uses, its demand will be highly elastic. For example, electricity.
(b) As against it, if commodity under consideration has only limited uses, its demand will be highly Inelastic.
7. Share in Total Expenditure:
(a) If a smaller proportion of consumer’s income is spent on a particular commodity, its elasticity is highly inelastic because lesser proportion of consumer income is spent on consumption of these commodities. Demand for goods like salt, needle, etc. tends to be inelastic as consum ers spend a small proportion of their income on such goods. When prices of such goods change, consumers continue to purchase almost the same quantity of these goods.
(b) As against it, if a larger proportion of consumer income is spent on the commodity, elasticity of demand is highly elastic.
8. Time Period: Price elasticity of demand for a commodity also affected by time period.
(a) Demand is inelastic in the short period as consumers find it difficult to change
their habits during short period.
(b) As against it, demand is highly elastic during long period as their is availability of close substitutes in long period.
9. Habits
(a) The demand for those goods that are habitually consumed is inelastic. The reason is that such commodities become a necessity for the consumer, and even if prices change, consumers continue to purchase and consume the commodity. Examples of habit-forming commodities include alcoholic beverages, tobacco (in its various forms) consumption and even tea and coffee.
(b) As against it, if a person is not habitual, demand is elastic.

Words that Matter

1. Elasticity of Demand: The degree of responsiveness of demand to the changes in determinants of demand (Price of the commodity, Income of a Consumer, Price of related commodity) is known as elasticity of Demand.
2. Price elasticity of Demand: The degree of responsiveness of quantity demanded to changes in price of commodity is known as price elasticity of Demand.
3. Percentage Method/Flux Method: According to this method, price elasticity of demand is measured by dividing the percentage change in quantity demand by the percentage change in price. 4. Unitary elastic demand: If percentage change in the quantity demanded is equal to percentage change in price of the commodity, then ED = 1 and the result is known as unitary elastic demand.
5. More than unitary elastic demand or elastic demand: If percentage change in quantity demanded is more than the percentage change in price of the commodity then, ED > 1 and result is known as more than unit elastic demand.
6. Less than unitary elastic demand or inelastic demand: If percentage change in quantity demanded is less than the percentage change in price of the commodity, then ED < 1 and the result is known as less than unit elastic demand.
7. Perfectly Elastic Demand: If quantity demand changes and price remains constant, then ED = Î±  and the result is known as perfectly elastic demand.
8. Perfectly Inelastic Demand: If price changes, and quantity demand remains constant, then ED = 0 and the result is known as perfectly Inelastic Demand.
9. Total expenditure method: It indicates the direction in which total expenditure on a product changes as a result of change in price of the commodity.
10. Geometric method or point method: According to point method, elasticity of demand at any point is measured by dividing the lower segment of demand curve with the upper segment of the demand curve at that point. It can be calculated by dividing the lower segment by upper segment.