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Chapter 6: Cross Elasticity of Demand (XED)

Part 6.1 – Understanding Cross Elasticity of Demand

By Dr. Anthony Fok

Introduction

Imagine Coca-Cola increases the price of Coke by 15%.

Will more consumers buy Pepsi?

Suppose Apple raises the price of the iPhone.

Will consumers switch to Samsung smartphones?

Now consider another situation.

If the price of petrol rises significantly, what happens to the demand for motor vehicles?

Or, if the price of coffee falls, what happens to the demand for sugar?

These examples illustrate an important economic relationship between different products.

Unlike Price Elasticity of Demand (PED), which examines how the demand for a product responds to changes in its own price, Cross Elasticity of Demand (XED) measures how the demand for one product responds to changes in the price of another product.

Businesses use XED extensively when analysing competitors, designing pricing strategies and forecasting sales.

Governments also use XED when evaluating the effects of taxation and regulation.

For A-Level Economics students, XED is an essential concept because it links consumer behaviour, market competition and strategic business decision-making.

What Is Cross Elasticity of Demand?

Cross Elasticity of Demand measures the responsiveness of the quantity demanded of one good to a change in the price of another good, assuming all other factors remain constant.

The formula is:

Cross Elasticity of Demand (XED) = Percentage Change in Quantity Demanded of Good A ÷ Percentage Change in Price of Good B

Unlike Price Elasticity of Demand, Cross Elasticity of Demand may be:

  • Positive
  • Negative
  • Zero

The sign itself provides important information about the relationship between the two products.

Why Is Cross Elasticity of Demand Important?

Businesses rarely operate in isolation.

Every firm competes with alternative products while simultaneously depending on complementary goods.

Understanding XED helps firms answer questions such as:

  • Who are our closest competitors?
  • How much market share could we lose if a rival cuts prices?
  • Which products should be bundled together?
  • How should we respond when competitors change prices?

Governments also consider XED when designing taxes on products such as fuel, tobacco and electric vehicles.

Positive Cross Elasticity of Demand

A positive XED indicates that the two products are substitutes.

When the price of one product increases, consumers switch to the other product.

Demand for the alternative product therefore increases.

Examples of Substitute Goods

Examples include:

  • Coca-Cola and Pepsi.
  • Apple iPhone and Samsung Galaxy smartphones.
  • Butter and margarine.
  • Grab and Gojek.
  • Starbucks and Coffee Bean.

These products satisfy similar consumer needs.

Consumers can often switch from one to another when relative prices change.

Singapore Example: Ride-Hailing Services

Suppose one ride-hailing platform increases its fares by 20%.

If another platform maintains lower prices, many commuters compare prices using mobile applications and choose the cheaper alternative.

Demand for the competing platform increases.

This demonstrates a positive Cross Elasticity of Demand.

The closer the substitutes, the larger the positive XED is likely to be.

Negative Cross Elasticity of Demand

A negative XED indicates that the products are complements.

Complementary goods are consumed together.

When the price of one product increases, demand for both products tends to decrease.

Examples of Complementary Goods

Examples include:

  • Cars and petrol.
  • Coffee and sugar.
  • Printers and printer ink.
  • Smartphones and mobile applications.
  • Game consoles and video games.

Consumers often purchase these products together.

Singapore Example: Motor Vehicles and Petrol

Suppose petrol prices increase substantially.

Some households may reduce car usage or postpone purchasing a new vehicle.

Consequently, demand for cars may decrease.

This demonstrates a negative Cross Elasticity of Demand between petrol and motor vehicles.

However, the strength of this relationship depends on factors such as public transport availability, household income and commuting needs.

Zero Cross Elasticity of Demand

Some products are unrelated.

A change in the price of one product has little or no effect on demand for the other.

These products have:

Cross Elasticity of Demand = 0

Examples include:

  • Toothpaste and umbrellas.
  • Bread and televisions.
  • School textbooks and bicycles.

Consumers generally make purchasing decisions independently.

Degrees of Cross Elasticity

Cross Elasticity varies in magnitude.

The numerical value helps businesses identify how closely products compete or complement one another.

High Positive XED

Products are very close substitutes.

Example:

Two brands of bottled mineral water.

A price increase for one brand may cause substantial switching.

Low Positive XED

Products are substitutes but not close substitutes.

Example:

Tea and coffee.

Some consumers switch, but many have strong preferences.

Large Negative XED

Products are consumed very closely together.

Example:

Printers and printer cartridges.

Demand for one product strongly influences demand for the other.

Small Negative XED

Products are complements but only loosely connected.

Example:

Cinema tickets and popcorn.

Some moviegoers purchase popcorn.

Others do not.

Business Applications of XED

Cross Elasticity of Demand is widely used in strategic decision-making.

Competitor Analysis

Businesses identify their closest competitors by estimating Cross Elasticity.

A high positive XED suggests strong competition.

Managers therefore monitor competitors’ pricing decisions carefully.

Pricing Strategy

Suppose a rival supermarket launches a major discount campaign.

If products exhibit high positive XED, competing supermarkets may respond by:

  • reducing prices,
  • increasing promotions,
  • introducing loyalty programmes,
  • expanding product differentiation.

Product Bundling

Complementary products are often sold together.

Examples include:

  • Smartphones with wireless earbuds.
  • Printers with ink cartridges.
  • Fast-food meals combining burgers, fries and drinks.

Bundling encourages consumers to purchase complementary goods simultaneously.

Government Applications

Governments also analyse Cross Elasticity when designing economic policies.

Environmental Policy

Suppose governments wish to reduce carbon emissions.

Higher taxes on petrol may encourage some consumers to purchase:

  • electric vehicles,
  • hybrid cars,
  • bicycles,
  • public transport services.

Understanding substitute relationships helps governments predict policy effectiveness.

Public Health

Governments introducing taxes on sugary drinks also consider whether consumers will switch towards:

  • bottled water,
  • sugar-free beverages,
  • fruit juice.

The effectiveness of taxation depends partly on Cross Elasticity between these products.

Dr. Anthony Fok’s Exam Tip

Students often memorise:

Positive = substitutes.

Negative = complements.

This alone is insufficient.

Always explain:

  • why consumers switch,
  • how the relationship affects demand,
  • whether the products are close or weak substitutes,
  • what factors influence the magnitude of XED.

The explanation earns more marks than simply stating the sign.

Common Student Mistake

❌ “A positive Cross Elasticity means demand increases.”

Not necessarily.

A positive XED simply indicates a substitute relationship.

Whether demand actually increases depends on which product’s price changes and in what direction.

Always analyse the specific scenario.

Worked Examination Example

Question

Samsung increases smartphone prices by 10%.

Demand for Apple iPhones increases by 8%.

Calculate the Cross Elasticity of Demand.

Solution

XED = Percentage Change in Quantity Demanded of Apple ÷ Percentage Change in Price of Samsung

= 8 ÷ 10

= +0.8

The positive value indicates that Apple and Samsung smartphones are substitute goods.

Because the value is less than one, they are substitutes, although consumers may not switch completely due to brand loyalty and product differentiation.

Quick Revision Summary

You should now be able to:

✓ Define Cross Elasticity of Demand.

✓ Calculate XED accurately.

✓ Distinguish substitutes from complements.

✓ Interpret positive, negative and zero values.

✓ Apply XED to business competition and government policy.

✓ Use Singapore examples to strengthen examination answers.

Coming Up in Part 6.2

The next section explores:

  • Determinants of Cross Elasticity of Demand.
  • Why some substitutes are stronger than others.
  • Factors affecting complementary goods.
  • Business competition strategies.
  • Singapore case studies.
  • Cambridge examination techniques.