1.2.4—Time periods

The short run is a period when at least one factor is fixed; in the long run all factors can be varied; the very long run also allows technology, institutions and population to change.

These are economic descriptions, not universal clock times. The relevant period depends on the decision and how fast inputs or capacity can adjust.

A restaurant may add staff in the short run but need the long run to expand its kitchen; over the very long run, cooking technology and consumer habits may change too.

Long run does not simply mean “a year” and does not guarantee that every adjustment is costless.