The fixed proportions law is also known as the law of proportionality. This law states that the proportion of inputs of factors used in a production process remain constant; when the quantity of one input is increased, the quantities of the other inputs are increased by the same proportion. In other words, any change in the proportion of inputs used to produce a given output will result in a proportional change in the output.
To illustrate, consider a car manufacturing firm that has a production process wherein the labour, capital and materials are used in a fixed proportion to produce cars. Further assume that the firm changes the investment in capital (by installing additional machines) but does not change the proportion of labour and materials used for production. Under such a situation, the firm would experience a proportional increase in output as the capital invested increases.
The fixed proportions law is based on the principle of substitution - a characteristic of all production systems. This principle states that a firm can substitute one factor of production for another but still get the same output, provided that the proportions in which the factors are substituted remain constant. For example, a firm which produces automobiles might substitute labour time for capital investment, as long as the proportion of labour time to capital investment remains constant.
The fixed proportions law is one of the key principles underlying production theory. It is an important concept not only because it helps us to understand the determinants of a firm’s output, but also because it provides an insight into how changes in the factors of production can effect an output.
The fixed proportions law is often referred to as the law of diminishing returns. This law suggests that as more of a certain input is used, the marginal output from that input begins to diminish. This is because any additional unit of an input will cause the production of less for every additional unit of that input, relative to the pre-existing fixed ratio of inputs.
In short, the fixed proportions law states that the proportion of inputs of factors used in a production process remain constant. It is based on the principle of substitution and is an important concept in production theory. Additionally, it is also referred to as the law of diminishing returns because it suggests that when more of an input is used, the marginal output from that input begins to diminish. Understanding this principle can help firms better understand the determinants of their output and how changes in their inputs can effect their production levels.