Questions: Zero-Profit Condition and Entry-Exit Dynamics

Question 1

A perfectly competitive bakery is earning zero economic profit. The owner says the business is doing great and has no reason to leave the industry. A classmate insists: 'Zero profit means it's failing — the bakery earns nothing!' Who is right?

• A. The classmate is right: zero profit means revenue barely covers costs, leaving nothing for the owner
• B. The owner is right: zero economic profit means the bakery earns a competitive return on all resources, including the owner's time and capital — the opportunity cost is fully covered
• C. Both are partially right: zero economic profit is healthy for the firm but signals the industry is stagnant
• D. The classmate is right: a rational owner would exit rather than earn zero profit

Answer: (B)

Zero *economic* profit is not the same as earning nothing. Economic profit is calculated after deducting all opportunity costs — including the implicit value of the owner's time and invested capital. A firm at zero economic profit earns exactly what those resources could earn in the next-best alternative. This is 'normal profit' — a competitive return that fully compensates the owner. There is no incentive to leave. The classmate confuses economic profit (which subtracts opportunity costs) with accounting profit (which doesn't).

Question 2

Demand for artisanal bread rises sharply, and competitive bakeries begin earning positive economic profit. Which sequence of events describes the long-run adjustment?

• A. Existing bakeries raise prices further to permanently capture the windfall
• B. New bakeries enter, industry supply expands, price falls until economic profit returns to zero
• C. Some bakeries exit, supply contracts, and higher profits persist indefinitely
• D. The government taxes excess profits to redistribute them to consumers

Answer: (B)

Positive economic profit signals that resources in this industry earn more than their opportunity cost — a magnet for new entrants. As firms enter, industry supply shifts right, driving price down. Entry continues until price falls to minimum LRATC and economic profit returns to zero, at which point the incentive to enter disappears. This self-correcting dynamic operates through individual firm incentives: no regulator or coordinator is needed.

Question 3

A competitive firm earning zero economic profit is still making a normal return on invested capital and the owner's time, and has no economic reason to exit the industry.

• T. True
• F. False

Answer: True

Zero economic profit is the equilibrium condition, not a sign of failure. Economic profit is calculated after subtracting all opportunity costs, including implicit costs of owner labor and capital. Zero economic profit means those resources are earning exactly what they could earn elsewhere — no better, no worse. Exit would mean redeploying resources for the same return, which gives no net gain. The firm is efficiently placed; it stays.

Question 4

In long-run competitive equilibrium, price equals minimum short-run average total cost but may exceed minimum long-run average total cost if the firm has economies of scale.

• T. True
• F. False

Answer: False

In long-run competitive equilibrium, five equalities hold simultaneously: P = minimum LRATC = minimum SRATC = SRMC = LRMC. The firm is at its efficient scale — the very bottom of the long-run average cost curve — and the short-run cost curve is tangent to the LRATC at that point. Price cannot exceed minimum LRATC in equilibrium: any positive economic profit would attract entry, expanding supply and driving price back down until all five equalities are restored.

Question 5

Explain why zero economic profit is the inevitable long-run destination of a competitive market, using the entry-exit mechanism.

Model answer: Positive economic profit attracts new entrants (resources earn more here than elsewhere), expanding industry supply and lowering price until profit reaches zero. Negative economic profit triggers exit (resources earn more elsewhere), contracting supply and raising price until losses are eliminated. Zero economic profit is the only point where neither entry nor exit is incentivized — the system rests there. Both forces are driven entirely by individual firms responding to their own profit signals.

The elegant feature of the zero-profit condition is that it emerges without coordination or regulation. Each firm acts in its own interest, and the aggregate of those decisions produces efficient resource allocation — the right quantity of industry output produced at the lowest possible cost per unit, sold at exactly that cost. The long-run supply curve's horizontal shape in a constant-cost industry is the graphical expression: society can get any quantity demanded at P = minimum LRATC, adjusting through entry and exit rather than price changes.