Demand (Edexcel IGCSE Economics)

Revision Note

Steve Vorster

Written by: Steve Vorster

Reviewed by: Jenna Quinn

Introduction to Demand

  • Demand is the amount of a good/service that a consumer is willing and able to purchase at a given price in a given time period

    • If a consumer is willing to purchase a good, but cannot afford to, it is not effective demand

  • A demand curve is a graphical representation of the price and quantity demanded (QD) by consumers

    • If data were plotted, it would be an actual curve.  Economists, however, use straight lines so as to make analysis easier

  • The law of demand states that there is an inverse relationship between price and quantity demanded (QD), ceteris paribus

    • When the price rises, the QD falls

    • When the price falls, the QD rises

Movement Along a Demand Curve

  • If price is the only factor that changes (ceteris paribus), there will be a change in the QD

    • This change is shown by a movement along the demand curve

Diagram: Movement Along a Demand Curve

Demand curve shows contraction in QD as prices increase & an extension in QD as prices decrease

A demand curve shows contraction in QD as prices increase and an extension in QD as prices decrease

Diagram analysis

  • An increase in price from £10 to £15 leads to a movement up the demand curve from point A to B

    • Due to the increase in price, the QD has fallen from 10 to 7 units

    • This movement is called a contraction in QD

  • A decrease in price from £10 to £5 leads to a movement down the demand curve from point A to point C

    • Due to the decrease in price, the QD has increased from 10 to 15 units

    • This movement is called an extension in QD

  • The law of demand captures this fundamental relationship between price and QD

    • It states that there is an inverse relationship between price and QD

      • When price rises, the QD falls

      • When prices fall, the QD rises

  • This relationship partly explains why the demand curve is downward sloping

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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.