Concept Architecture
Concept
Theoretically, Income Elasticity of Demand measures the responsiveness of the quantity demanded of a good or service to changes in consumer income, holding all other factors constant. It is a fundamental concept in consumer demand theory and is used to classify goods as normal, inferior, necessities, or luxuries. In health economics, income elasticity of demand is used to examine how healthcare utilisation, insurance coverage, pharmaceuticals, and preventive services respond to changes in household income.
Mathematically, income elasticity of demand is defined as the percentage change in quantity demanded divided by the percentage change in income. A positive elasticity indicates a normal good, while a negative elasticity indicates an inferior good. Values greater than one indicate luxury goods, whereas values between zero and one indicate necessities.
In practice, income elasticity is estimated using household expenditure surveys, healthcare utilisation databases, insurance claims, or national health surveys. Econometric demand models are used to estimate elasticity coefficients, which support forecasting, equity analyses, health financing policy, and evaluations of the effects of economic growth on healthcare demand.
Purpose
Used to quantify the responsiveness of demand for healthcare goods and services to changes in income, supporting demand forecasting, health financing, pricing policy, and equity analysis.
Mathematical Formulae
Primary Formula
E? = %?Q / %?Y
where:
- E? = income elasticity of demand
- %?Q = percentage change in quantity demanded
- %?Y = percentage change in income
Supporting Formulae
Arc income elasticity:
E? = [(Q? ? Q?) / ((Q? + Q?) / 2)] � [(Y? ? Y?) / ((Y? + Y?) / 2)]
Related Mathematical Methods
- Elasticity estimation
- Consumer demand modelling
- Econometric regression
- Demand forecasting
- Household expenditure analysis
Example
Average annual household income increases from �40,000 to �44,000, a 10% increase. Demand for preventive health screening rises from 1,000 to 1,120 appointments, a 12% increase.
E? = 12% / 10% = 1.2
An income elasticity of 1.2 indicates that preventive health screening behaves as a luxury good in this population.
Excel Implementation
| Function | Example Formula | Health Economics Application |
|---|---|---|
=((New-Old)/Old) | =(C2-B2)/B2 | Calculates the percentage change in quantity demanded. |
=((New-Old)/Old) | =(E2-D2)/D2 | Calculates the percentage change in income. |
/ | =((C2-B2)/B2)/((E2-D2)/D2) | Calculates income elasticity of demand. |
| LINEST | =LINEST(LN(Quantity),LN(Income),TRUE,TRUE) | Estimates income elasticity using log-linear demand models. |
VBA (Optional)
Automate estimation of income elasticities for multiple healthcare services and classify them as normal, inferior, necessity, or luxury goods.
Sources
- Varian HR. Intermediate Microeconomics: A Modern Approach.
- Pindyck RS, Rubinfeld DL. Microeconomics.
- Folland S, Goodman AC, Stano M. The Economics of Health and Health Care.
- Zweifel P, Breyer F, Kifmann M. Health Economics.
- Drummond MF, et al. Methods for the Economic Evaluation of Health Care Programmes. Oxford University Press.
Related Concepts (2)
Library
Publications
1
Uncertainty and the Welfare Economics of Medical Care — Kenneth J. Arrow, Vol. 53, No. 5 ed., 1963 (American Economic Review)
The founding paper of health economics as a discipline, analysing how uncertainty, asymmetric information, trust and the special features of medical markets prevent them from behaving like ordinary competitive markets — the intellectual origin of the entire field.
Journal ArticleView source →
Frequently Asked Questions (6)
What is the income elasticity of demand?
A measure of how quantity demanded responds to a change in consumer income, calculated as percentage change in demand over percentage change in income.
Source: Varian 2014
How is income elasticity of demand calculated?
Income elasticity of demand is found by dividing the percentage change in the quantity demanded of a good by the percentage change in consumer income that brought it about. Because both are proportional changes, the result is a unit-free number whose sign and size summarise the response. A positive value means demand rises with income, a negative value means it falls, and a value above one means demand rises more than in proportion to income. Varian (2014) sets out this calculation.
Source: Varian 2014
What do different values of income elasticity mean?
A positive income elasticity means the good is normal, with demand rising as income rises; a negative value means the good is inferior, with demand falling as income rises. Among normal goods, an elasticity greater than one marks a luxury, whose demand rises proportionally more than income, while a value between zero and one marks a necessity, whose demand rises but less than proportionally. The value thus classifies the good by how its demand responds to income.
Source: Varian 2014
How does income elasticity of demand distinguish normal from inferior goods?
A normal good is one whose demand rises as income rises, giving a positive income elasticity, as with most goods people buy more of when better off. An inferior good is one whose demand falls as income rises, giving a negative income elasticity, because consumers switch to preferred alternatives as they can afford them. The distinction depends on how demand responds to income, and a good may be normal for some consumers or income ranges and inferior for others.
Source: Varian 2014
By income elasticity of demand, is health care a normal or luxury good?
Studies of the income elasticity of health care spending suggest it is a normal good, with demand rising as income rises, and at the level of whole countries its elasticity has often been estimated near or above one, which would make aggregate health care resemble a luxury. Estimates vary with the level of analysis and method, and individual demand may appear more like a necessity. The question matters for predicting how health spending grows as economies become richer.
Source: Varian 2014
Why is income elasticity of demand useful?
Income elasticity of demand is useful for predicting how demand for a good will change as incomes change, which informs forecasting, planning, and policy. It indicates whether demand for a good will grow or shrink with rising prosperity, and by how much, and it classifies goods as necessities, luxuries, or inferior. For health care, estimates of income elasticity help anticipate how spending will evolve as national income grows, which bears on the sustainability of health systems.
Source: Varian 2014
Trust Record
Verified by Dr Darrin Baines
British health economist
Professional identity: darrinbaines.org
Verification date: 10 Sep 2025
Content version: 1.0.0
Canonical Identity
- Term code
- HE-EE-ME-028
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