<P> In microeconomics, the long run is the conceptual time period in which there are no fixed factors of production, so that there are no constraints preventing changing the output level by changing the capital stock or by entering or leaving an industry . The long run contrasts with the short run, in which some factors are variable and others are fixed, constraining entry or exit from an industry . 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 . </P> <P> In the long run, firms change production levels in response to (expected) economic profits or losses, and the land, labour, capital goods and entrepreneurship vary to reach the minimum level of long - run average cost . In the simplified case of plant capacity as the only fixed factor, a generic firm can make these changes in the long run: </P>

Economists define the short run as a period of time so short that
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