Intermediatemicroeconomics
The Shutdown Decision: When to Stop Producing
Overview
Should a losing firm keep producing or shut down? This lesson derives the short-run shutdown rule: produce if P ≥ min AVC, shut down if P < min AVC. You will see why fixed costs are irrelevant to the decision, locate the shutdown point where MC crosses AVC, and contrast the short-run shutdown with the long-run exit decision.
Learning objectives
- State and derive the short-run shutdown rule P ≥ min AVC.
- Explain why fixed (sunk) costs do not affect the shutdown decision.
- Locate the shutdown point on the cost diagram.
- Distinguish short-run shutdown from long-run exit.
The Question: Produce at a Loss or Shut Down?
A firm whose price lies below ATC is losing money - but shutting down does not erase fixed costs, which must be paid anyway in the short run. The real choice is between two losses: operating loss = (ATC - P)·Q versus shutdown loss = TFC. The firm should pick the smaller loss, and that comparison reduces to a beautifully simple rule about variable costs.
Shutdown means producing zero while keeping the plant - paying fixed costs and waiting for better prices. Exit means leaving the industry and avoiding fixed costs too. This lesson covers shutdown; exit follows in market structure lessons.
Deriving the Rule: P vs AVC
Operating loses (ATC - P)·Q; shutting down loses TFC = (AFC)·Q. Operating is better when (ATC - P)·Q < AFC·Q, i.e., when ATC - P < AFC, i.e., when P > ATC - AFC = AVC. So: produce if P ≥ min AVC, shut down if P < min AVC. If price covers average variable cost, revenue pays all variable costs plus part of fixed costs - better than paying all fixed costs with zero revenue.
Short run: produce if P ≥ minimum AVC; shut down if P < minimum AVC. Fixed costs cancel out of the comparison - only variable costs matter.
The Shutdown Point on the Diagram
Minimum AVC is where MC crosses AVC - so the shutdown point is the MC/AVC intersection, at price P = min AVC and quantity Q_sd. Above that price the firm's supply curve is its MC curve; below it, quantity supplied is zero. The supply curve thus starts at the shutdown point and follows MC upward - a construction every competition diagram relies on.
Why Fixed Costs Are Ignored
Fixed costs are sunk in the short run: paid whether the firm produces or not, they cannot change the ranking of the two options. Including them would wrongly suggest shutting down whenever P < ATC - yet a firm with P between AVC and ATC loses less by operating, since revenue covers variable costs and contributes toward fixed costs. This is the sunk-cost principle applied to production.
Losses alone never justify shutdown. Between min AVC and min ATC the firm loses money overall but loses less than the full fixed cost - operating is the smaller evil. Only P < min AVC triggers shutdown.
Short-Run Shutdown vs Long-Run Exit
In the long run all costs are variable - there are no fixed costs to be stuck with - so the rule hardens: exit if P < min ATC (equivalently, min LRAC). A firm that rationally weathers a bad quarter (P above AVC) will still leave the industry if low prices persist and it cannot cover total costs when its plant comes up for renewal. Shutdown is riding out the storm; exit is abandoning the ship.
Shutdown in Real Markets
Airlines park planes but keep leases during demand slumps; restaurants close for renovation months while paying rent; oil wells are capped when crude falls below lifting costs. Each is the rule in action: variable costs uncovered, fixed costs honored, reopening when prices recover. The rule also explains why supply can vanish suddenly - once price crosses min AVC, quantity drops to zero, not just a little.
Key points
- Short-run shutdown rule: produce if P ≥ min AVC; shut down if P < min AVC.
- Operating at P between AVC and ATC loses money but less than the fixed cost - so operate.
- Fixed (sunk) costs are paid either way and cancel out of the decision.
- The shutdown point is the MC/AVC intersection; the supply curve starts there.
- Long-run exit rule: leave if P < min ATC, since all costs are variable in the long run.
- Shutdown is temporary (plant kept); exit is permanent (plant abandoned).
Common misconceptions
✓ Truth: Losses relative to total cost are not the test - the test is price versus average variable cost. Covering variable costs and contributing anything toward fixed costs beats shutting down and eating the full fixed cost.
✓ Truth: Shutdown is a temporary zero-output pause with the plant retained; the firm still exists and pays fixed costs. Going out of business - exit - is the distinct long-run decision.
✓ Truth: That crossing is minimum ATC, relevant for long-run exit. The shutdown point is the lower MC/AVC crossing - minimum average variable cost.
Practice questions
Q1. A firm's min AVC is $8 and min ATC is $12. The market price is $10. In the short run the firm should:
- shut down.
- produce, since P > min AVC.
- exit the industry.
- produce only if MC is falling.
P = 8), so revenue covers variable costs and contributes $2 per unit toward fixed costs - a smaller loss than shutting down and paying full fixed costs. (In the long run, P < min ATC would prompt exit.)
Q2. The shutdown point on a cost diagram is located where:
- MC crosses ATC.
- MC crosses AVC at its minimum.
- AVC crosses ATC.
- MC is at its minimum.
Minimum AVC occurs at the MC/AVC intersection (marginal-average rule). That price is the threshold: below it the firm supplies zero; above it, supply follows MC.
Q3. Why are fixed costs excluded from the shutdown decision?
- Because they are always zero.
- Because they must be paid whether the firm produces or not, so they don't affect the comparison.
- Because they exceed variable costs.
- Because accountants handle them separately.
Shutdown compares operating losses against the fixed costs paid anyway. Since TFC appears on both sides, it cancels - the decision turns entirely on whether revenue covers variable costs.
Q4. In the long run, a competitive firm exits the industry if:
- P < min AVC.
- P < min ATC (min LRAC).
- P > MC.
- accounting profit is zero.
With all inputs variable, there are no unavoidable fixed costs, so the firm must cover total costs to justify staying. Persistent P below minimum average total (long-run) cost means exit.
Click a question to reveal the answer and explanation.
Frequently asked questions
What if price exactly equals minimum AVC?
The firm is indifferent: operating loses exactly TFC, the same as shutting down. By convention economists say the firm is willing to produce (the rule uses ≥). In practice, tiny frictions decide - but the indifference itself is the point.
Do real firms actually compute min AVC before shutting down?
Roughly, yes: managers compare expected price against avoidable (variable) costs - fuel, crew, materials - and idle capacity when price won't cover them. Airlines, shipping, and mining apply this logic continuously.
Why doesn't the rule use marginal cost instead of AVC?
It does, indirectly: the firm produces the P = MC quantity whenever it produces at all. The AVC comparison answers the prior question - produce at all, or zero? - and min AVC is exactly where the P = MC quantity becomes viable.
Can a firm shut down in the long run?
The long-run analogue is exit: with no fixed costs, any persistent P < min ATC means leaving the industry. 'Shutdown' specifically means zero output with fixed costs still being paid - a purely short-run situation.