Marginal product

In economics and in particular neoclassical economics, the marginal product or marginal physical product of an input (factor of production) is the change in output resulting from employing one more unit of a particular input (for instance, the change in output when a firm's labor is increased from five to six units), assuming that the quantities of other inputs are kept constant.

The marginal product of a given input can be expressed as:

where ${\displaystyle \Delta X}$ is the change in the firm's use of the input (conventionally a one-unit change) and ${\displaystyle \Delta Y}$ is the change in quantity of output produced (resulting from the change in the input). Note that the quantity ${\displaystyle Y}$ of the "product" is typically defined ignoring external costs and benefits.

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