Q.Explain the Law of Variable Proportions.
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Start your 14-day free trial to unlock the full solution →As a variable factor is increased on a fixed factor, marginal product rises, then diminishes, then turns negative — the Law of Variable Proportions.
This 8-mark item is a key short-run production law in CHSE Odisha +2 Business Economics (aligned with the NCERT/CBSE curriculum).
Meaning. In the short run, at least one factor (say land or plant) is fixed while others vary. When successive units of the variable factor (labour) are combined with the fixed factor, the proportion between them changes, and output behaves in a definite pattern. This is the Law of Variable Proportions (also called the Law of Non-proportional Returns, the modern form of the Law of Diminishing Returns).
Assumptions.
- The state of technology is given and unchanged.
- One factor is fixed and others are variable (short run).
- All units of the variable factor are equally efficient (homogeneous).
- Factors can be combined in varying proportions.
Illustration (a hypothetical schedule). With land fixed at 1 acre and labour varied:
| Labour (units) | Total Product (TP) | Marginal Product (MP) | Average Product (AP) |
|---|---|---|---|
| 1 | 10 | 10 | 10 |
| 2 | 24 | 14 | 12 |
| 3 | 39 | 15 | 13 |
| 4 | 50 | 11 | 12.5 |
| 5 | 56 | 6 | 11.2 |
| 6 | 57 | 1 | 9.5 |
| 7 | 57 | 0 | 8.1 |
| 8 | 54 | −3 | 6.75 |
Three stages of production.
- Stage I — Increasing returns: TP rises at an increasing rate and MP rises (up to the 3rd unit here). Better utilisation of the fixed factor and division of labour raise efficiency. AP also rises.
- Stage II — Diminishing returns: TP continues to rise but at a diminishing rate; MP falls but stays positive until it becomes zero, where TP is at its maximum (7th unit, TP = 57). This is the most important stage — a rational producer operates here, because MP and AP are both positive but falling. The fixed factor is now being over-used relative to the variable factor. …
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