Short Run

What Is the Short Run?

In economics, the short run is a period during which a business cannot change at least one of its inputs. That fixed input is usually physical capital, such as a factory, a building, or heavy equipment. The short run is defined by this constraint rather than by a set length of time, so its duration differs across industries and companies. The long run is the contrasting case, in which every input can be adjusted.

How the Short Run Works

During the short run, a firm changes its output mainly by adjusting variable inputs, such as hourly labor, raw materials, and energy. It generally cannot quickly add a new plant or buy a large new machine. Because of this limit, adding more workers to a fixed set of machines eventually produces smaller gains in output, a pattern economists call diminishing marginal returns. The production function describes this relationship between inputs and output.

Costs follow a similar pattern. Some costs, known as fixed costs, are owed regardless of how much the firm produces, while variable costs rise and fall with output. Economists also study marginal cost, the added cost of producing one more unit, to judge how much to produce in the short run.

An Example

Consider a bakery with a single oven. In the short run, the owner can hire extra bakers, buy more flour, and schedule longer shifts to produce more bread. The owner cannot quickly install a second oven, which would take time and money. Once the oven runs at full capacity, extra workers add less and less to total output because they must share the same equipment. If demand grows enough, the owner may expand the bakery, and at that point the business has moved into the long run.

Why It Matters to Investors

The short run helps explain why profits can change sharply when sales move. A company with large fixed costs keeps paying those expenses when revenue falls, so a modest drop in sales can have a large effect on earnings. Analysts often compare how much of a company's cost base is fixed with how much is variable when assessing its sensitivity to changes in demand. These are general economic ideas that describe how cost structures behave, not predictions of any particular company's results.