Is there a specific amount of time that distinguishes the long run from the short run? Is the amount of time important? Explain.

No, the length of time constituting the long run varies substantially by industry, so we do not think in terms of a specific number of years, months, or days. A firm's profits and losses guide business managers toward decisions about entry into or exit from the industry. The long run has occurred once firms have had sufficient time to enter or leave based on profits or losses in the industry and economic profits are zero.