Profit, Loss, and the Shutdown Decision

After finding the output where $P=MC$, compare price with average costs. If $P>ATC$, the firm earns positive economic profit. If $P=ATC$, economic profit is zero. If $P<ATC$, the firm incurs a loss, but loss alone does not imply immediate shutdown.

The short-run shutdown rule

Fixed cost must be paid in the short run whether the firm produces or not. Producing is better than shutting down when revenue covers variable cost:

When $AVC<P<ATC$, the firm produces at a loss because it covers all variable cost and contributes something toward fixed cost. Shutting down would lose the entire fixed cost. If $P<\min AVC$, production cannot cover avoidable operating cost, so shutdown minimizes loss.

Shutdown is not exit

Shutdown is a short-run decision to produce zero while retaining fixed capacity and paying unavoidable fixed cost. Exit is a long-run decision to leave the market when commitments can be ended. Persistent $P<ATC$ encourages exit because all costs become avoidable in the long run.

At exactly minimum AVC, the firm is indifferent between operating and shutting down in the simplified model. Real decisions may include restart costs, worker retention, spoilage, contracts, reputation, and uncertainty.

Graphically, profit or loss at positive output is

This rectangle measures total profit, while $P-AVC$ measures contribution per unit toward fixed cost.

Compare the three price zones

At the chosen output of 20, suppose AVC is 6 and ATC is 10. At price 12, the firm earns $2\times20=40$. At price 8, it loses $2\times20=40$, but each unit contributes 2 toward fixed cost; shutting down would lose the full fixed cost of 80. At price 4, revenue fails to cover variable cost, so producing loses more than shutting down.

This gives three zones: profit above ATC, loss-minimizing production between AVC and ATC, and shutdown below AVC. Drawing price lines across the cost curves makes the logic visible.

Think forward at shutdown

Fixed cost that cannot be avoided today should not be “recovered” by producing units that make the loss larger. The firm compares operating profit with the shutdown payoff. In the long run, leases and capacity may become avoidable, so persistent failure to cover ATC encourages exit.

Real firms also consider restart costs, customer relationships, perishable inventory, worker retention, and uncertainty. These details modify the threshold but do not change the basic principle: compare avoidable benefits and costs over the relevant horizon.