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# CA Foundation | Theory of Consumer Behaviour | Chanakya Commerce Classes

CA Foundation Paper 4 Business Economics Theory of Consumer Behaviour chapter-wise study material for May 2026 exam onwards by Chanakya Commerce Classes.

Canonical URL: https://www.chanakyaclasses.com/notes/theory-of-consumer-behaviour

CA Foundation · Paper 4 · Business Economics
Theory of
Consumer Behaviour
Unit 2 · Chapter 2 · MCQ-focused revision sheet for May 2026 exam onwards
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Study material aligned with the current Business Economics section.
All Economics Units
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Theory of
Consumer Behaviour
Unit 2 · Chapter 2 · MCQ-focused revision sheet for May 2026 exam onwards
MCQ Priority
Concept Clarity
Quick Revision
Crux First
What you must remember for MCQs
Utility = satisfaction from consumption.
Marginal utility falls as consumption rises.
Consumer buys till
MU = Price
.
Consumer Surplus = extra benefit over actual price paid.
Indifference Curve shows consumer preferences.
Consumer equilibrium under IC analysis =
MRS = Price Ratio
.
1. Human Wants
Meaning
Want means a
desire to consume goods or services
.
Features of Wants
Wants are unlimited.
Each want is satiable.
Wants are competitive because resources are limited.
Wants may be complementary, like car and fuel.
Wants are subjective and relative.
They depend on income, fashion and habits.
Classification of Wants
Necessaries
For survival: food, shelter
For efficiency: education, health
Conventional: based on social customs
Comforts
Improve the standard of living
Luxuries
Not essential and usually expensive
MCQ Trap
The same good can shift category over time depending on income, habits and living standards.
2. Utility
Meaning
Utility means the
want satisfying power
of a good.
It does not mean moral usefulness.
Utility is psychological and subjective.
Types of Utility Measure
Total Utility (TU)
= total satisfaction from all units consumed.
Marginal Utility (MU)
= extra satisfaction from one more unit.
TU = Σ MU
MU = ΔTU
3. Relation between TU and MU
When TU rises, MU keeps falling gradually.
When TU is maximum, MU becomes zero.
When TU starts falling, MU becomes negative.
Situation
Result
At first unit
TU = MU
MU falling
TU rises at a decreasing rate
MU = 0
TU is maximum
MU negative
TU falls
4. Law of Diminishing Marginal Utility
Meaning
As a consumer consumes more units of a commodity, the
extra satisfaction from each additional unit falls
.
Only MU falls. TU does not immediately fall.
Key Logic
Wants are satiable.
Intensity of want reduces with consumption.
Assumptions
Units consumed are the same.
Consumption is continuous.
No change in taste or income.
Units are standard.
Law applies generally, though exceptions exist.
Exceptions
Money
Gold
For some goods, desire may keep rising instead of falling.
5. Consumer Surplus
Meaning
Consumer surplus means the
extra benefit
that a consumer gets over and above the price actually paid.
Consumer Surplus = Willingness to Pay − Actual Price
Key Concept
It is based on the law of diminishing marginal utility.
The consumer buys till
MU = Price
.
Graph Insight
Consumer surplus is the area below the demand curve and above the price line.
Effect of Price
Price rises → Consumer surplus falls
Price falls → Consumer surplus rises
Applications
Pricing decisions
Tax policy
Welfare measurement
Price discrimination
Limitations
Utility cannot be measured exactly.
Marginal utility of money may not remain constant.
Difficult to apply perfectly in real life.
6. Indifference Curve Analysis
Indifference curve analysis is more realistic than utility analysis.
The consumer compares
combinations of goods
, not utility numbers.
Assumptions
Consumer is rational.
Consumer has complete knowledge.
Preferences can be ranked.
Preferences are consistent and transitive.
More is better.
7. Indifference Curve
Meaning
An indifference curve shows all combinations of two goods that give the
same level of satisfaction
.
The consumer is indifferent between all points on the same curve.
It is also called an
iso-utility curve
.
8. Marginal Rate of Substitution (MRS)
Meaning
MRS is the rate at which one good is exchanged for another while keeping satisfaction unchanged.
MRS = MUx / MUy
Key Concept
MRS diminishes as the consumer moves down an indifference curve.
Reason:
As the consumer gets more of X, desire for additional X falls, so willingness to sacrifice Y also falls.
9. Properties of Indifference Curve
Downward sloping
Convex to the origin
Never intersect each other
Higher indifference curve means higher satisfaction
Do not touch the axes
Special Cases
Perfect substitutes
→ straight line IC
Perfect complements
→ L-shaped IC
10. Budget Line
Meaning
Budget line shows all combinations of two goods that the consumer can afford.
PXQX + PYQY = Income
Key Points
Slope of budget line = price ratio
It shows the consumer’s constraint
Changes in Budget Line
Income rises → budget line shifts right
Price changes → slope changes
11. Consumer Equilibrium
Condition
Consumer is in equilibrium where the
budget line is tangent to the indifference curve
.
At equilibrium:
MRS = Price Ratio
MUx / MUy = Px / Py
Meaning
The consumer gets maximum satisfaction.
There is no incentive to change the chosen combination.
Final 1-Minute Revision
Strict exam recall points
MU falls = key law of consumer behaviour.
TU maximum when MU = 0.
Consumer surplus = extra benefit.
Indifference curve = equal satisfaction combinations.
MRS diminishes.
Budget line = affordability line.
Consumer equilibrium = MRS = Px/Py.
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CA Foundation · Paper 4 · Business Economics · Unit 2: Theory of Consumer Behaviour
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