Introduction to Laws of Diminishing Return
The Law of Diminishing Returns is a fundamental principle in economics that describes how, in the short run, increasing a variable factor (such as labour) while keeping other factors constant (such as land or capital) leads to a decline in the marginal product of the variable factor after a certain point.
This law is a part of the Law of Variable Proportions and applies to short-run production, where at least one factor remains fixed.
Definition
The Law of Diminishing Returns states that as more units of a variable input (e.g., labour) are added to a fixed input (e.g., land or capital), the marginal product of the variable input will initially increase, then decrease, and eventually become negative.
Key Assumptions
- Short Run – At least one factor of production (like land or capital) is fixed.
- Homogeneous Units of Input – Each additional unit of the variable factor is identical in skill and efficiency.
- Technology Remains Constant – No improvements in technology.
- Fixed Scale of Production – Only the variable factor changes.
Explanation with Table
Let’s take the example of a small farm where land is fixed at 10 acres, and the farmer increases the number of labourers to observe the change in output.
| Labour (Workers) | Total Product (TP) (kg of crops) | Marginal Product (MP) | Stage of Production |
|---|---|---|---|
| 1 | 50 | 50 | Increasing Returns (Stage I) |
| 2 | 120 | 70 | Increasing Returns (Stage I) |
| 3 | 180 | 60 | Increasing Returns (Stage I) |
| 4 | 220 | 40 | Diminishing Returns (Stage II) |
| 5 | 250 | 30 | Diminishing Returns (Stage II) |
| 6 | 270 | 20 | Diminishing Returns (Stage II) |
| 7 | 280 | 10 | Diminishing Returns (Stage II) |
| 8 | 280 | 0 | Maximum TP (End of Stage II) |
| 9 | 270 | -10 | Negative Returns (Stage III) |
| 10 | 250 | -20 | Negative Returns (Stage III) |
Stages of Production in the Law of Diminishing Returns
The table above illustrates how production changes as we increase labour. It can be divided into three distinct stages:
- Stage I: Increasing Returns (MP Rises)
- As more workers are added, total output increases at an increasing rate because resources are underutilized.
- Example: From 1 to 3 workers, MP is increasing (50 → 70 → 60).
- Stage II: Diminishing Returns (MP Declines but Positive)
- Additional workers increase total production but at a decreasing rate due to resource limitations.
- Example: From 4 to 7 workers, MP decreases from 40 to 10, but TP is still increasing.
- Stage III: Negative Returns (MP Becomes Negative)
- Too many workers lead to inefficiencies, congestion, and overuse of fixed resources, causing total production to decline.
- Example: After 8 workers, TP stagnates and then falls, with MP turning negative (-10, -20).
Graphical Representation
The Law of Diminishing Returns can be illustrated with a Total Product (TP), Marginal Product (MP), and Average Product (AP) curve (similar to the first image you uploaded).
- TP Curve: Initially rises, then slows down, peaks, and eventually falls.
- MP Curve: Rises in Stage I, declines in Stage II, and becomes negative in Stage III.
- AP Curve: Follows a similar trend but does not become negative.
Real-World Examples
- Agriculture – Adding more workers to a fixed-size farm initially increases yield, but after a point, overcrowding reduces efficiency.
- Manufacturing – A factory with limited machines can improve productivity by adding workers, but excessive workers lead to inefficiencies.
- Restaurants – Increasing chefs in a small kitchen initially boosts output, but too many chefs create congestion and inefficiency.
Conclusion
The Law of Diminishing Returns highlights the optimal level of input usage in production. It helps businesses determine the ideal number of workers or resources to use before productivity starts declining. Recognizing this law allows managers to balance efficiency and costs, ensuring optimal resource allocation.