Key Concepts and Summary
In the long run, firms will respond to profits through a process of entry, where existing firms expand output and new firms enter the market. Conversely, firms will react to losses in the long run through a process of exit, in which existing firms reduce output or cease production altogether. Through the process of entry in response to profits and exit in response to losses, the price level in a perfectly competitive market will move toward the zero-profit point, where the marginal cost curve crosses the AC curve, at the minimum of the average cost curve.
The long-run supply curve shows the long-run output supplied by firms in three different types of industries: constant cost, increasing cost, and decreasing cost.
the long-run process of firms entering an industry in response to industry profits
the long-run process of firms reducing production and shutting down in response to industry losses
where all firms earn zero economic profits producing the output level where P = MR = MC and P = AC