# WHAT IS PRICE ELASTICITY OF DEMAND

**WHAT IS PRICE ELASTICITY OF DEMAND**

Price elasticity of demand, also known as the co-efficient of price elasticity, may be the degree of responsiveness of the demanded of a commodity to change in of the commodity.

In other words, it is of responsiveness of quantity demand small change in the price of the co-efficient the ratio of the percentage change in quantity demanded to the percentage change in Elasticity of demand is expressed ma as follows:

Elasticity of Demand (ED)

= Percentage change in demand

Percentage change in price

= **% DQd**

%Dp

Where D = Change

Qd = Quantity demanded

P = price

## Types of price elasticity of demand

- Elastic Demand: Demand is said to be elastic if small change in price leads to a greater change in the quantity of goods demanded. In this case, elasticity is greater than one or unitary, i.e. E = > 1< infinity. This type of elasticity can also be described as fairly elastic demand.

- Inelastic demand: Demand is said to elastic if a larger change in price leads to a or slight change in the quantity of goods demanded. In this case elasticity is less than but greater than zero, i.e. E => 0 < 1. This type o f elasticity can also be described as fairly tic demand.

- Unity or unitary elastic demand: Demand is said to be unitary when a change in price leads to an equal change in the quantity of goods demanded. In other words, a 5% change in price will lead to a 5% change in demand. In this situation elasticity is equal to one, i.e E = 1.

**Perfectly elastic demand or infinitely**elastic demand: Demand is said to be perfectly elastic when a change in price brings about an infinite effect on the quantity of goods demanded. In other words, a slight increase in price can make consumers to stop the purchase of the commodity while a slight decrease in price will make consumers to purchase all the commodities. In this case, elasticity is equal to infinity.

**Perfectly inelastic demand or zero**elastic demand: Demand is said to be perfectly inelastic if a change in price has no effect whatsoever on the quantity of goods demanded. In other words, the same quantity of goods is demanded irrespective of changes in price. In this case elasticity is equal to zero, i.e. E = 0

**How to measure elasticity of demand**

Elasticity of demand can be measured or calculated by using the co-efficient of price elasticity of demand. The formula used in calculating the elasticity of demand is:-

= Elasticity of Demand (ED)

Percentage change in price

= %DQd

%DP

Where D = change

Qd = Quantity demanded

P = Price

As explained earlier, when

- Elasticity is equal to one, elasticity of demand is unity.
- Elasticity is greater than one, elasticity of demand is elastic.
- Elasticity is less than one, elasticity of demand is inelastic.

Examples 1

The price of bread in 2002 was increased from 6 40 to 6 50 and the quantity bought per week by a consumer decreased from 160 loaves to 80.

- Present the above data in a table.
- Calculate the co-efficient of price el of demand.
- What type of elasticity is this and how did you arrive at your conclusion.

Solution

(a)

Price (6) | Quantity Demanded |

40 50 | 160 80 |

(b)(i) Percentage change in quantity demanded

= Change in Qd x 100

Old QD 1

= (160 – 80) x 100

160 1

= 80 x 100

160 1

= 50%

(ii) Percentage changes in price

= Change in price x 100

Old in price

= (650 – 640) x 100

640 1

= 10 x 100

40 1

= 25%

### Co-efficient of price elasticity of demand

ED = 50%

25% = 2

- The co-efficient of elasticity of demand is elastic. It is elastic because elasticity is greater than 1.

Example 2

Given the figures below:

Price of commodity A in January = 5.00

Price of commodity A in February = 6 7.00

Quantity of A bought in January = 20kg

Quantity of A bought in February = 16kg

(a) Calculate:

(i) Percentage change in quantity bought (%)

(ii) Percentage change in price of A (%)

- Co-efficient of price elasticity of demand

- From your answer
- Is the demand elastic or inelastic?
- How do you know this?

Solution

Commodity A

Month | Price | Qty. demanded |

January | 65 | 20kg |

February | 67 | 16kg |

(a)(i) Percentage change in quantity demanded

= Change Qd x 100

Old Qd 1

= (20 – 16) x 100

20 1

= 4 x 100

20 1

= 20%

(ii) Percentage change in price of A

= Change in price x 100

Old price 1

= (7 – 5) x 100

5 1

= 2 x 100

5 1

= 40%

Co-efficient of price elasticity

ED = Percentage change in qty. demanded

Percentage change in price

ED = 20%

40%

= ½ or .05

(b)(i) Demand is inelastic

(ii) 0.5 or ½ is less than one. Hence, the co-efficient of price elasticity of demand is inelastic.

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