What is the cause behind the convexity of indifference curve to the origin?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Law of Diminishing Marginal Rate of Substitution
A consumer with many bananas and few mangoes will give up several bananas for one more mango. As bananas become scarce and mangoes plentiful, the consumer gives up fewer and fewer bananas for each further mango while staying equally satisfied. This amount is the marginal rate of substitution (MRS), and its steady fall is the law of diminishing marginal rate of substitution.
Because the MRS falls, the indifference curve becomes flatter as we move down along it, and that is what makes it convex to the origin.
Why the other options are incorrect
Option (2) Law of Demand — Incorrect. It relates the price of a good to the quantity demanded; it explains the slope of the demand curve, not the shape of an indifference curve.
Option (3) Law of Variable Proportion — Incorrect. It is a law of production: the marginal product of one variable input first rises and then falls.
Option (4) Cardinal Utility Analysis — Incorrect. It measures utility in numbers. Indifference curves belong to ordinal utility analysis, which only ranks bundles.
Note: A same/similar question was asked in CUET (UG) in the papers below.
| 2026 | 2025 | 2024 | 2023 | 2022 |
| 15-05 S1 | 14-05 S1* | – | 13-06 S1* | – |
* A similar question.
NCERT (2025-26): “2.1.2 Ordinal Utility Analysis … So, with increase in the number of bananas, the consumer will feel the inclination to sacrifice small and smaller amounts of mangoes. This tendency for the MRS to fall with increase in quantity of bananas is known as Law of Diminishing Marginal Rate of Substitution.… …It may be mentioned that the law of Diminishing Marginal Rate of Substitution causes an indifference curve to be convex to the origin. This is the most common shape of an indifference curve.…” |