Indifference Curves & Budget Lines (Cambridge (CIE) A Level Economics): Revision Note

Indifference curves

• An indifference curve shows all the combinations of two goods that give a consumer the same level of satisfaction

• If a person is equally happy with different combinations, those combinations lie on the same curve

  • For example, when choosing between cinema tickets and video game hours, one combination might be 2 cinema tickets and 3 hours of gaming, while another might be 3 tickets and 1 hour of gaming. If both options feel equally enjoyable, they lie on the same indifference curve

• Higher indifference curves = more happiness

• Rational consumers aim for the highest curve they can afford

How the curve works

• Indifference curves slope downwards. This means that if someone gives up one unit of a good (like a cinema ticket), they need more of the other (like gaming time) to stay just as satisfied

• So if the consumer moves from 3 tickets and 1 hour of gaming to 2 tickets and 3 hours of gaming, they are still on the same curve and their happiness has not changed

Budget lines: making smart spending choices

• A budget line shows all the combinations of two goods a consumer can afford, given their income and the price of the goods

• It helps explain how people make choices when their money is limited

What shifts the budget line?

• If income decreases the whole line shifts inward from BL1 to BL2 as less of both goods can be bought

• If the price of cinema tickets increases, the line pivots inward from BL1 to BL3 on the cinema tickets axis, as less tickets can be bought with the same income

Limitations of the indifference curve model

While indifference curves are useful for showing how consumers choose between two goods, the model has several real-world limitations

1. Real-life choices involve more than two goods

• In reality, consumers do not just choose between two items. A student deciding how to spend their weekly allowance might be weighing up clothes, snacks, streaming subscriptions, school supplies, and transport costs, not just two items

2. People often express preferences, not indifference

• The term “indifference” suggests that a person is equally happy with any combination of the two goods on the curve

• Consumers tend to have clear preferences. For example, one student might strongly prefer three cinema tickets and one book over two books and one cinema ticket, even if both combinations lie on the same curve

• This challenges the idea that people are truly indifferent between combinations

3. Consumers do not always behave rationally

• Indifference curves assume that people make logical decisions to maximise their satisfaction. Real behaviour does not always follow this pattern

• A student might spend all their money on limited-edition trainers even if they need school supplies. They might impulsively buy concert tickets instead of saving for a trip

• Emotional decisions, peer pressure, and habits often override rational thinking