Consider the following statements: Other things remaining unchanged, market demand for a good might increase if 1. price of its substitute increases 2. price of its complement increases 3. the good is an inferior good and income of the consumers increases 4. its price falls Which of the above statements are correct?
Contents15
- A1 and 4 only
- B2, 3 and 4
- C1, 3 and 4
- D1, 2 and 3
Show answer
Answer: (A) 1 and 4 only
Statement 1 is correct:
Substitutes are goods used in place of each other (e.g., tea and coffee).
If coffee's price rises, people switch to tea, so tea's demand increases.
Demand for a good rises when its substitute's price rises.
Statement 2 is wrong:
Complements are goods used together (e.g., tea and sugar).
If sugar's price rises, people buy less tea too.
So a rise in complement's price decreases demand — not increases it.
Statement 3 is wrong:
An inferior good is one whose demand falls when income rises (e.g., coarse cereals).
The question asks about goods whose demand increases — that describes normal goods, not inferior goods.
Statement 4 is correct:
This is the basic Law of Demand — when a good's price falls, its demand increases (other things being equal).
Statements 1 and 4 are correct.
Answer: (a).
Basic demand theory concepts like substitutes, complements, and inferior goods form the foundation for understanding market behavior and price mechanisms.
UPSC tests whether students can distinguish between factors that increase versus decrease demand, particularly the tricky concept that inferior goods behave opposite to normal goods when income changes.
Types of Goods: Economic Classification
Indian Economy substitute complement inferior good
Types of Goods: Economic Classification & UPSC Traps
Substitute goods: demand rises when substitute's price rises (tea-coffee)
Complement goods: demand falls when complement's price rises (tea-sugar)
Inferior goods: demand falls when income rises (coarse cereals)
Normal goods: demand rises when income rises (branded items)
Understanding Economic Goods
Economists classify goods based on how their demand responds to changes in price of related goods and consumer income. These classifications help predict market behavior and form the foundation of demand theory.
Classification by Relationship
Type | Definition | Price Effect | Example |
|---|---|---|---|
Substitute Goods | Used in place of each other | Substitute's price ↑ → Good's demand ↑ | Tea-Coffee, Bus-Train |
Complement Goods | Used together | Complement's price ↑ → Good's demand ↓ | Tea-Sugar, Car-Petrol |
Independent Goods | No relationship | No cross-effect on demand | Books-Shoes |
Classification by Income Response
Type | Income Effect | Consumer Behavior | Indian Examples |
|---|---|---|---|
Normal Goods | Income ↑ → Demand ↑ | Buy more when richer | Branded clothes, smartphones |
Inferior Goods | Income ↑ → Demand ↓ | Switch to better alternatives | Coarse cereals, public transport |
Luxury Goods | Income ↑ → Demand ↑↑ | High income elasticity | Cars, premium products |
Question Connection
Statement 3 was the key trap: it confused inferior goods (demand falls with income rise) with normal goods (demand rises with income rise). The question asked when demand increases — eliminating inferior goods immediately.
Trap: Confusing substitute vs complement effects — remember substitutes have positive cross-elasticity, complements have negative cross-elasticity
Trap: Statement 3 reverses inferior good behavior — inferior goods have falling demand when income rises
Trap: UPSC often tests whether you know the direction of demand change, not just the relationship
Law of Demand & Demand Determinants
Indian Economy market demand price falls
Law of Demand & Factors Affecting Market Demand
Law of Demand: Price ↓ → Quantity demanded ↑ (other things equal)
5 key determinants: Price of good, substitute prices, complement prices, income, preferences
Market demand: sum of all individual demands at each price level
Core Concept
The Law of Demand states that quantity demanded varies inversely with price, assuming ceteris paribus (other things remaining unchanged). Market demand is influenced by multiple factors beyond the good's own price.
Determinants of Demand
# Market Demand
## Price Factors
- Own price (Law of Demand)
- Substitute prices (+)
- Complement prices (-)
## Consumer Factors
- Income level
- Tastes & preferences
- Expectations
## Market Factors
- Number of buyers
- Seasonal factors
- Government policiesHow Demand Changes Work
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`**Change in Determinant**
Price, income, or related good price changes`"]
s2["`**Consumer Response**
Buying behavior adjusts based on economic logic`"]
s3["`**Market Effect**
Individual responses aggregate to market demand shift`"]
s4["`**New Equilibrium**
Market finds new price-quantity balance`"]
s1 --> s2
s2 --> s3
s3 --> s4PYQ Application
This question tested 4 different determinants: substitute prices (✓), complement prices (✗), income effects for inferior goods (✗), and own price (✓). Only statements 1 and 4 correctly described demand increases.
Trap: Own price vs market demand — price fall increases quantity demanded, but economists often test this as 'demand increase'
Trap: Direction confusion — always check whether the question asks for demand increase or decrease
Trap: Ceteris paribus violations — UPSC may give scenarios where multiple factors change simultaneously
Cross-Price Elasticity of Demand
Indian Economy
Cross-Price Elasticity: Measuring Inter-Good Relationships
Cross-price elasticity = % change in demand of Good A / % change in price of Good B
Positive coefficient = substitute goods, Negative coefficient = complement goods
Zero coefficient = independent goods with no relationship
Economic Significance
Cross-price elasticity measures how responsive one good's demand is to another good's price change. The sign of the coefficient reveals the economic relationship between goods.
Elasticity Interpretation
Coefficient | Relationship | Market Response | Business Implication |
|---|---|---|---|
Positive (+) | Substitute goods | Rival's price ↑ → My demand ↑ | Competitive pricing strategy |
Negative (-) | Complement goods | Partner's price ↑ → My demand ↓ | Joint marketing needed |
Zero (0) | Independent goods | No cross-effect | Separate market strategies |
High absolute value | Strong relationship | Large demand shifts | High market interdependence |
Real-World Applications
Pricing decisions: Companies monitor substitute prices to set competitive rates
Market entry: High cross-elasticity indicates intense competition in the segment
Government policy: Tax on complements affects demand for both goods
Demand forecasting: Changes in related good prices help predict sales
PYQ Connection
Statements 1 and 2 directly tested cross-price elasticity understanding. Substitute relationship (positive elasticity) increases demand, while complement relationship (negative elasticity) decreases demand when the related good's price rises.
Trap: Sign confusion — positive cross-elasticity means substitute, negative means complement
Trap: UPSC may give numerical cross-elasticity values and ask you to identify the relationship type
Trap: Don't confuse cross-price elasticity with own-price elasticity of demand