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What is the 'Long Run'

The long run is a period of time in which all factors of production and costs are variable. In the long run, firms are able to adjust all costs, whereas, in the short run, firms are only able to influence prices through adjustments made to production levels. Additionally, whereas firms may be a monopoly in the short-term, they may expect competition in the long-term.

In economics, long-run models may shift away from short-turn equilibrium, in which supply and demand react to price levels with more flexibility.



The long run is a time period over which a manufacturer or producer is flexible on his or her production decisions. For example, a business with a one-year lease will have its long run defined as any period longer than a year since it’s not bound by the lease agreement after a year. In the long run, the amount of labor, size of the factory, and production processes can be altered if need be. Businesses can either expand or reduce production capacity, or enter or exit an industry based on expected profits. Firms examining the long run understand that they cannot alter levels of production in order to reach an equilibrium between supply and demand.

In response to expected economic profits, firms can change production levels. For example, a firm may implement change by increasing (or decreasing) the scale of production in response to profits (or losses), which may entail building a new plant or adding a production line.

The short run, on the other hand, is the time horizon over which factors of production are fixed, except for labor which remains variable.

In macroeconomics, the long run is the period when the general price level, contractual wage rates, and expectations adjust fully to the state of the economy, in contrast to the short run when these variables may not fully adjust.

Long Run Costs

As explained above, the scale of production can change in the long run, which means that all costs are variable in the long run. In the long run, a firm will search for the production technology that allows it to produce the desired level of output at the lowest cost. If a company is not producing at its lowest cost possible, it may lose market share to its competitors which are able to produce and sell at minimum cost.

Economies of scale refers to the situation where, as the quantity of output goes up, the cost per unit goes down. In effect, economies of scale are the cost advantages that are achieved when there is an expansion of the size of production. The cost advantages translate to improved efficiency in production, which can give a business a competitive advantage in its industry of operations, which in turn, could translate to lower costs and higher profits for the business.

The long run is associated with the long-run average total cost (LRAC), the average cost of output feasible when all factors of production are variable. The LRAC curve is the curve along which a firm would minimize its cost per unit for each respective long-run quantity of output. As long as the long run average cost curve (LRAC) is declining, then internal economies of scale are being exploited. If LRAC is falling when output is increasing, then the firm is experiencing economies of scale. When LRAC eventually starts to rise then the firm experiences diseconomies of scale, and, if LRAC is constant, then the firm is experiencing constant returns to scale.

The long-run average cost (LRAC) curve is comprised of a group of short-run average cost (SRAC) curves, each of which represents one specific level of fixed costs. The long-run average cost curve will, therefore, be the least expensive average cost curve for any level of output.

Market Entry and Exit in the Long Run

The number of firms in an industry is variable in the long run, as competitors may enter or exit an industry depending on the levels of profit previously seen by companies operating in that industry. A firm may decide to enter a market in response to expected profits, or exit a market in response to expected losses. The profit expectations in a market may be due to a change in consumers’ sensitivity to price changes, thus, price elasticity of demand in the long run may vary.

Conversely, barriers to entry prevent competitors from quickly entering a market in the short run.

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