The law of diminishing returns explains how the additional output gained from increasing a variable factor of production eventually falls when at least one factor remains fixed. It applies to the short run, where firms cannot immediately change all of their factors of production. Understanding diminishing returns is important for A-Level Economics students because it helps explain changes in productivity, marginal product and marginal costs as firms increase their use of variable factors.
This topic can be found in:
- AQA A-Level Economics | Component 1: Individuals, Firms, Markets and Market Failure | Topic 4: Production, Costs and Revenue
Definitions
- Short run: A period of time where at least one factor of production is fixed.
- Long run: A period of time where all factors of production are variable.
- Total product: The total output produced using a given quantity of inputs.
- Marginal product: The additional output produced from using one more unit of a variable factor.
- Law of diminishing returns: The principle that adding more units of a variable factor to a fixed factor will eventually cause marginal product to fall.
Key Features
The Short Run and Fixed Factors
The law of diminishing returns applies in the short run, where at least one factor of production is fixed. For example, a firm may have a fixed amount of machinery, factory space or land while increasing the number of workers. In the short run, the firm can increase the intensity with which its existing capacity is used, but it cannot immediately increase all factors of production.
Changes in Marginal Product
As more units of a variable factor are added to a fixed factor, marginal product may initially increase because workers can specialise and make better use of the fixed factor. However, the fixed factor eventually becomes constrained, meaning that each additional unit of the variable factor contributes less additional output. For example, adding workers to a factory may initially increase output significantly, but eventually there may not be enough machinery or space for each additional worker to work effectively.
Diminishing Returns and Marginal Costs
Once diminishing returns occur, marginal product falls because additional units of the variable factor produce progressively less additional output. This can cause marginal costs to rise because the firm needs to use more variable inputs to produce each additional unit of output. Therefore, the law of diminishing returns helps explain why a firm's marginal cost may eventually increase as output rises.
Evaluation
Advantages
- Explains Changes in Productivity: The law of diminishing returns helps explain why marginal product may initially rise but eventually falls as more variable factors are added to a fixed factor.
- Explains Rising Marginal Costs: Diminishing marginal product means that more variable inputs are required to produce additional output, helping explain why marginal costs can eventually rise.
- Supports Production Decisions: Understanding diminishing returns can help firms decide how intensively to use their existing factors of production in the short run.
Disadvantages
- Only Applies in the Short Run: The law of diminishing returns applies where at least one factor is fixed, so it does not explain how output changes when all factors can be varied.
- Depends on Fixed Factors: Diminishing returns occur because a variable factor is being added to a fixed factor. If the firm changes its scale in the long run, the relationship between inputs and output is considered through returns to scale instead.
- Initial Productivity May Increase: The addition of variable factors does not necessarily cause diminishing returns immediately. Marginal product may initially increase because of specialisation and more effective use of fixed factors.
Summary
- The law of diminishing returns applies to the short run, where at least one factor is fixed.
- Total product measures total output, while marginal product measures additional output from one more variable factor.
- Marginal product may initially increase because of specialisation and better use of fixed factors.
- Eventually, adding more variable factors causes marginal product to fall as the fixed factor becomes constrained.
- Diminishing returns can cause marginal costs to rise because more variable inputs are needed to produce additional output.
0 comments