What Is the Marginal Product of Labor?

The marginal product of labor (MPL) is an important concept in economics that measures how much additional output a firm can produce by employing one more unit of labor, while keeping other factors of production constant. It helps businesses understand the contribution of individual workers and plays a major role in decisions about hiring, wages, and production.

In simple terms, the marginal product of labor answers the question: “How much more can a business produce if it hires one additional worker?”

Definition of the Marginal Product of Labor

The marginal product of labor is the change in total output resulting from a one-unit increase in the amount of labor used, assuming other inputs remain unchanged.

It can be expressed using the following formula:

MPL = Change in Total Product ÷ Change in Labor

For example, suppose a bakery has five employees and produces 500 loaves of bread per day. If hiring a sixth employee increases production to 560 loaves, the marginal product of the sixth worker is:

MPL = (560 − 500) ÷ (6 − 5) = 60 loaves

Therefore, the sixth worker contributes an additional 60 loaves per day.

Marginal Product and Total Product

To understand marginal product, it is useful to distinguish it from total product. Total product is the overall quantity of goods or services produced by a firm using a particular combination of inputs.

Marginal product, by contrast, focuses only on the additional output created by an additional unit of an input.

For example, imagine a small factory with the following production levels:

The marginal product is calculated by comparing each worker's contribution with the output produced before that worker was hired. The second worker, for example, increases output from 20 to 45 units, so the second worker's marginal product is 25 units.

This example also demonstrates that marginal product does not necessarily remain constant.

The Law of Diminishing Marginal Returns

One of the most important ideas associated with marginal product is the law of diminishing marginal returns. This law states that when additional units of a variable input, such as labor, are added to fixed inputs, the marginal product will eventually decline.

Consider a restaurant with a small kitchen. Hiring a second or third employee may significantly increase production because workers can divide tasks efficiently. However, if the restaurant keeps hiring workers without expanding the kitchen, employees may eventually get in each other's way.

As a result, each additional worker contributes less additional output than the previous worker.

Initially, the marginal product may actually increase because workers can specialize and cooperate more effectively. Eventually, however, the fixed resources—such as machinery, workspace, or equipment—become constraints, causing marginal product to fall.

Diminishing marginal returns are particularly important for firms because they help determine how many workers should be employed.

Marginal Product of Labor and Wages

The marginal product of labor is closely connected to a firm's willingness to hire workers. In a competitive market, a firm generally compares the value of the additional output produced by a worker with the cost of employing that worker.

If the price of the firm's product is $10 per unit and an additional worker produces 20 more units, the worker adds:

20 × $10 = $200

to the firm's revenue, assuming all 20 units can be sold at that price.

This additional revenue is called the marginal revenue product of labor (MRP).

In a simplified competitive market:

MRP of Labor = Marginal Product of Labor × Price of Output

A profit-maximizing firm will generally continue hiring workers as long as the additional revenue generated by the next worker is at least as large as the worker's additional cost.

Thus, marginal product helps connect production decisions to labor demand.

Why Does Marginal Product Change?

Several factors can affect the marginal product of labor.

1. Amount of Capital

Workers often need machines, tools, computers, or other equipment to produce goods and services. If a company has plenty of productive equipment, an additional worker may be highly productive.

For example, adding an employee to a factory with modern machinery may substantially increase output. However, if the factory has too few machines, workers may have to wait for equipment, reducing their marginal product.

2. Worker Skills and Training

More skilled or experienced workers generally have a higher marginal product because they can perform tasks more efficiently.

Training can therefore increase the marginal product of labor by improving workers' productivity.

3. Technology

Technological improvements can increase how much output workers can produce. A new software system, faster machine, or automated tool may allow employees to complete more work in the same amount of time.

Consequently, improvements in technology can increase the marginal product of labor.

4. Organization of Production

How workers are organized can also affect productivity. Specialization and division of labor can allow employees to focus on particular tasks and become more efficient.

Poor organization, on the other hand, can reduce the contribution of additional workers.

Marginal Product Versus Average Product

Marginal product should not be confused with average product of labor.

The average product of labor measures output per worker:

Average Product = Total Product ÷ Quantity of Labor

For example, if 10 workers produce 1,000 units, the average product is 100 units per worker.

Marginal product measures the additional output generated by the next worker.

The two measures are related. If the marginal product of a new worker is greater than the existing average product, the average product will tend to rise. If the marginal product is below the average product, the average product will tend to fall.

A Practical Example

Suppose a farm has a fixed amount of land. With one worker, it produces 100 kilograms of crops. Adding a second worker increases production to 220 kilograms. The second worker therefore has a marginal product of 120 kilograms.

A third worker increases production to 330 kilograms, giving that worker a marginal product of 110 kilograms.

A fourth worker raises production to 420 kilograms, producing a marginal product of 90 kilograms.

The marginal product has started to decline because the amount of land remains fixed while more workers are using it.

This illustrates diminishing marginal returns: adding labor increases total production, but each additional worker eventually contributes a smaller amount of additional output.

Why the Marginal Product of Labor Matters

The marginal product of labor is useful to businesses, economists, and policymakers because it provides insight into worker productivity and labor demand.

For businesses, it can help determine whether hiring another employee is economically worthwhile. If an additional worker generates significant extra revenue, hiring may increase profits. If the worker adds very little output while costing a substantial amount to employ, hiring may not be profitable.

For economists, marginal product helps explain why firms demand labor and why changes in productivity can influence wages and employment.

For workers, productivity can also matter because firms have stronger incentives to pay higher wages when employees can generate more valuable output.

Conclusion

The marginal product of labor is the additional output produced when a firm employs one more unit of labor while holding other inputs constant. It is calculated by dividing the change in total output by the change in labor.

MPL is a fundamental concept because it connects the production decisions of firms with their decisions about employment. It also helps explain the law of diminishing marginal returns, the relationship between productivity and labor demand, and why factors such as technology, capital, training, and organization can affect worker productivity.

Ultimately, understanding marginal product of labor helps explain a basic economic question: how much additional value does one more worker bring to a firm's production process? The answer can influence how many workers a firm hires, how much it is willing to pay them, and how efficiently it operates.