Chapter 5: Income Elasticity of Demand (YED)
Part 5.2 – Determinants of Income Elasticity of Demand, Business Applications and Singapore Examples
By Dr. Anthony Fok
Introduction
In Part 5.1, we learnt that Income Elasticity of Demand (YED) measures how responsive demand is to changes in consumer income.
However, not all goods respond in the same way.
Why does demand for luxury holidays increase rapidly when incomes rise, while demand for rice barely changes?
Why do some discount retailers perform well during recessions while luxury boutiques struggle?
Why do businesses carefully monitor GDP growth, employment and household income before making investment decisions?
The answer lies in the determinants of Income Elasticity of Demand.
Understanding these determinants enables firms to forecast demand more accurately, governments to anticipate changes in consumption patterns and students to provide deeper explanations in examinations.
What Determines Income Elasticity of Demand?
Several factors influence how demand changes when income changes.
The main determinants include:
- Whether the product is a necessity or luxury.
- Availability of higher-quality alternatives.
- Consumer preferences.
- Income level of consumers.
- Stage of economic development.
- Time period.
Unlike Price Elasticity of Demand, YED is primarily influenced by how consumers prioritise spending when their purchasing power changes.
1. Nature of the Good
The most important determinant is whether the product is regarded as a necessity or a luxury.
Necessities
Necessities satisfy basic daily needs.
Examples include:
- Rice
- Bread
- Fresh vegetables
- Electricity
- Water
- Basic healthcare
- Public transport
As income rises, consumers usually purchase only slightly more of these goods.
For example, a household earning S$5,000 per month does not consume five times as much rice as a household earning S$1,000 per month.
Consequently, necessities generally have:
Positive YED less than 1
Luxury Goods
Luxury goods provide additional comfort, prestige or enjoyment rather than basic survival.
Examples include:
- Luxury cars
- Five-star hotels
- Business-class air travel
- Designer handbags
- Fine dining
- Premium home renovations
As income increases, consumers often allocate a disproportionately larger share of additional income towards these products.
Therefore:
Luxury goods usually have YED greater than 1.
Singapore Example: Overseas Holidays
During periods of strong economic growth, many Singaporean households increase spending on overseas travel.
Families may:
- travel more frequently,
- choose longer holidays,
- upgrade from economy to business class,
- stay in higher-end hotels.
These changes illustrate the relatively high income elasticity of demand for international tourism.
Conversely, during recessions, overseas holidays are often among the first expenditures to be reduced.
2. Availability of Better Alternatives
As income rises, consumers often substitute lower-quality products with premium alternatives.
This influences whether a product is classified as an inferior good.
Example
A university student initially purchases budget instant coffee.
After securing a higher-paying job, she begins purchasing premium coffee from specialty cafés.
Demand for premium coffee increases.
Demand for budget coffee decreases.
The availability of better alternatives contributes to the negative YED of some lower-priced products.
3. Consumer Preferences
Consumer tastes change over time.
Higher incomes often increase demand for:
- healthier food,
- environmentally friendly products,
- organic produce,
- personalised services,
- premium educational programmes.
Therefore, changes in preferences may strengthen the income elasticity of certain products.
Singapore Example: Organic Food
As household incomes have increased, many consumers have become more willing to purchase organic vegetables, premium dairy products and sustainably sourced seafood.
Although these products are more expensive, higher incomes enable consumers to place greater emphasis on health and quality.
4. Income Level
YED may differ across income groups.
Lower-Income Households
Additional income is often spent on necessities.
Examples include:
- groceries,
- healthcare,
- education,
- transportation.
Higher-Income Households
Once basic needs have been satisfied, additional income is more likely to be spent on:
- luxury holidays,
- investments,
- premium experiences,
- high-end consumer products.
This explains why luxury industries often target affluent consumers.
5. Stage of Economic Development
Income elasticity also varies between developing and developed economies.
Developing Economies
As incomes rise from relatively low levels:
Demand for:
- refrigerators,
- washing machines,
- motor vehicles,
- smartphones
often increases rapidly.
Developed Economies
In higher-income countries such as Singapore, many households already own these products.
Future income growth may therefore generate smaller increases in demand.
Instead, consumers may spend additional income on:
- experiences,
- healthcare,
- financial investments,
- retirement planning,
- premium services.
6. Time Period
Consumer behaviour evolves over time.
Immediately following an increase in income, households may save a significant portion of their additional earnings.
As confidence improves, spending gradually increases.
Businesses therefore distinguish between:
- short-run demand,
- long-run demand.
This distinction often strengthens evaluation in examination answers.
Business Applications of YED
Income Elasticity of Demand is widely used in business decision-making.
Forecasting Sales
Businesses analyse economic forecasts before deciding:
- production levels,
- staffing requirements,
- inventory,
- expansion plans.
If economists predict strong income growth, firms selling luxury products may expect demand to increase substantially.
Investment Decisions
Investors also consider YED.
Luxury retailers generally perform better during economic expansions.
Discount retailers may perform relatively well during economic downturns.
Understanding YED therefore assists investment analysis.
Market Segmentation
Companies design different products for different income groups.
For example:
An automobile manufacturer may produce:
- entry-level models,
- mid-range vehicles,
- luxury models.
Each targets consumers with different income levels and spending behaviour.
Government Applications
Governments also use YED extensively.
Forecasting Tax Revenue
Higher household income generally increases spending.
This may generate:
- higher Goods and Services Tax (GST) revenue,
- increased corporate profits,
- greater income tax collections.
Governments incorporate these projections into budget planning.
Infrastructure Planning
Suppose household incomes are expected to rise steadily.
Demand for:
- airports,
- public transport,
- tourism facilities,
- recreational amenities
may also increase.
Governments therefore use YED when planning long-term infrastructure investment.
Singapore Case Study: Private Healthcare
As incomes increase, many Singapore residents choose:
- private medical consultations,
- specialist clinics,
- private hospital wards,
- comprehensive health screening packages.
Demand for premium healthcare services often increases faster than income, reflecting a relatively high YED among higher-income households.
However, public healthcare remains essential for many households, demonstrating that different healthcare services may exhibit different income elasticities.
Dr. Anthony Fok’s Exam Tip
Students frequently write:
“Income increased, so demand increased.”
This explanation is incomplete.
Instead, explain:
- whether the product is a necessity or luxury,
- why consumers allocate additional income to the product,
- whether alternative products exist,
- whether different income groups behave differently.
This deeper analysis distinguishes stronger examination answers.
Common Student Mistake
❌ “Luxury goods always have the same YED.”
Incorrect.
Income elasticity varies according to:
- consumer income,
- economic conditions,
- market characteristics,
- cultural preferences.
For example, premium smartphones may have a high YED among younger professionals but a lower YED among retirees who already own suitable devices.
Always analyse the specific context.
Worked Examination Example
Question
Singapore’s economy is forecast to grow by 4% next year.
Explain how this may affect demand for:
- Public transport.
- Luxury cruises.
Model Answer
Demand for public transport is likely to increase only modestly because it is a necessity with a positive YED less than one.
Demand for luxury cruises is likely to increase proportionately more than income because cruises are generally regarded as luxury services with a YED greater than one.
However, the extent of the increase depends on consumer confidence, exchange rates and household expectations about future income.
Quick Revision Summary
By the end of this section, you should be able to:
- Explain the determinants of Income Elasticity of Demand.
- Distinguish necessities from luxury goods using YED.
- Analyse how businesses use YED for forecasting and planning.
- Explain how governments apply YED in policy-making.
- Apply YED to Singapore examples.
- Strengthen examination answers with balanced evaluation.
Coming Up in Part 5.3
The next section will examine:
- Income Elasticity of Demand and the business cycle.
- YED in recessions and economic expansions.
- Industry analysis using YED.
- Business strategy based on income changes.
- Singapore case studies.
- Cambridge essay and Case Study Question techniques.