The Significance of PED (Cambridge (CIE) O Level Economics)

Revision Note

Steve Vorster

Written by: Steve Vorster

Reviewed by: Jenna Quinn

PED and Total Revenue

  • Revenue is the amount of money a firm receives from selling its goods/services

    • Total revenue = price x quantity

  • The total revenue rule states that in order to maximise revenue, firms should increase the price of products that are inelastic in demand and decrease prices on products that are elastic in demand 

  • This can be illustrated using a demand curve

An illustration of price elastic demand where a small decrease in price from P1→P2 causes a large increase in quantity demanded from Q1→ Q2
An illustration of price elastic demand where a small decrease in price from P1→P2 causes a large increase in quantity demanded from Q1→ Q2

Diagram analysis

  • The demand curve is very elastic in this market

  • When a good/service is price elastic in demand, there is a greater than proportional increase in the quantity demanded to a decrease in price

  • Total revenue is higher once the price has been decreased

    • left parenthesis straight P subscript 2 cross times straight Q subscript 2 right parenthesis space greater than space left parenthesis straight P subscript 1 cross times straight Q subscript 1 right parenthesis

Graph showing price (vertical axis) vs. quantity (horizontal axis) with a downward sloping demand curve labeled D1. Prices P1 and P2 align with quantities Q1 and Q2.
An illustration of price inelastic demand where a large increase in price from P1→P2 causes a small decrease in quantity demanded from Q1→ Q2

Diagram analysis

  • The demand curve is very inelastic in this market

  • When a good/service is price inelastic in demand, there is a smaller than proportional decrease in the quantity demanded to an increase in price

  • Total revenue is higher once the price has been increased

    • left parenthesis straight P subscript 2 cross times straight Q subscript 2 right parenthesis space greater than space left parenthesis straight P subscript 1 cross times straight Q subscript 1 right parenthesis

Worked Example

A firm raises the price of its products from £10 to £15. Sales have fallen from 100 to 40 units per day. Explain if they made the correct decision

Step 1: Calculate the initial sales revenue

Sales space Revenue space equals space Price space of space product space straight X space Quantity space sold
space space space space space space space space space space space space space space space space space space space space space space space space space equals £ 10 space straight x space 100
space space space space space space space space space space space space space space space space space space space space space space space space space equals space £ 1 comma 000

Step 2: Calculate the sales revenue after the price change

Sales space Revenue space equals space Price space of space product space straight X space Quantity space sold
space space space space space space space space space space space space space space space space space space space space space space space space space equals £ 15 space straight x space 40
space space space space space space space space space space space space space space space space space space space space space space space space space equals space £ 600


Step 3: Explain the decision

By raising the price, the total revenue has fallen by £400. This indicates that the product is price elastic in demand and the firm should have lowered their price in order to maximise revenue

Examiner Tips and Tricks

A common error students make is to say that when prices increase and the product is inelastic in demand, the quantity demanded does not fall. It does! But it is a less than proportional fall than the increase in price. 

So, when Governments tax demerit goods such as cigarettes, the increase in price is greater than the decrease in QD, but QD still falls.

The Implications of PED for Stakeholders

  • Knowledge of PED is important to firms seeking to maximise their revenue

    • If their product is price inelastic in demand, they should raise their prices

    • If price elastic in demand, then they should lower their prices

    • Firms can choose to use price discrimination to maximise their revenue i.e. lower prices for certain segments and higher prices for others

  • Knowledge of PED is important to Governments with regard to taxation and subsidies

    • If they tax price inelastic in demand products, they can raise tax revenue without harming firms too much

    • Consumers are less responsive to price changes so firms will pass on the tax to the consumer

    • If Governments subsidise price elastic in demand products, there can be a greater than proportional increase in demand

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Steve Vorster

Author: Steve Vorster

Expertise: Economics & Business Subject Lead

Steve has taught A Level, GCSE, IGCSE Business and Economics - as well as IBDP Economics and Business Management. He is an IBDP Examiner and IGCSE textbook author. His students regularly achieve 90-100% in their final exams. Steve has been the Assistant Head of Sixth Form for a school in Devon, and Head of Economics at the world's largest International school in Singapore. He loves to create resources which speed up student learning and are easily accessible by all.

Jenna Quinn

Author: Jenna Quinn

Expertise: Head of New Subjects

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.