Excess Capacity: Zero Profit, Markup and Minimum ATC

Zero profit does not imply competitive efficiency.

Read Two Model-Based Comparisons

Use the standard smooth long-run model here: differentiated products, entry and exit, a downward-sloping demand curve for each firm and a U-shaped average total cost curve. The chosen positive output is a profit maximum. The efficiency comparison assumes that the model’s prices and costs capture the relevant marginal benefits and resource costs; it is not a measurement of every real industry.

Locate the Long-Run Tangency

At the standard long-run equilibrium, the firm’s demand curve touches ATC at its chosen output. Demand and ATC have the same value there, so price equals average total cost. With downward-sloping demand, the tangency lies on the declining part of the U-shaped ATC curve. The firm therefore produces less than the output at minimum ATC, even though no positive economic profit remains.

Measure an Output Gap, Not Idle-Machine Hours

Excess capacity is the gap between the firm’s long-run equilibrium output and the output that minimizes ATC. It does not mean machines literally sit idle every hour or that producing at minimum ATC would be profitable given the firm’s demand. It is a cost-curve comparison showing the firm operates left of efficient scale.

Explain Why Zero Profit Can Coexist with a Markup

At tangency, P=ATC but demand slopes downward, so MR lies below price. Because the firm sets MR=MC, it follows that P>MC. Zero economic profit therefore coexists with markup and allocative inefficiency. The absence of excess profit does not make the outcome perfectly competitive.

Include the Value of Differentiated Choice

Consumers may value variety, convenience, innovation and a product that better matches their needs. The conventional graph identifies a unit-cost gap and a price–marginal-cost gap for the modeled product; it does not settle whether eliminating differentiation would improve welfare. A complete comparison must also consider the value of variety and any costs or benefits omitted from the model.

Identify the Advertising Channel

Advertising can supply information or create perceived differentiation. If it informs buyers about price, quality, or location, it may improve matching and intensify competition. If it mainly strengthens brand loyalty, it can make demand less elastic and increase markup. Economics exam questions ordinarily specify the mechanism. “advertising always raises welfare” and “advertising is always wasteful” are both too broad.

Read the Standard-Model Reference

Keep the Original Café’s Profit and Markup Separate

In the standard long-run model, a café’s demand is tangent to ATC at 200 drinks per period and a $5 price. ATC is $5, so total revenue and economic cost are both $1,000; economic profit is zero. MC is $3.80, leaving a $1.20 price–MC gap. That gap is not $1.20 of net profit on each drink: average total cost, not marginal cost, belongs in the profit calculation. The tangency implies output below minimum ATC under the stated model, but the exact capacity gap cannot be calculated until the minimum-ATC quantity is given.

Include Advertising’s Relevant Cost

Evaluate advertising’s revenue and cost changes together. An informative message can help buyers compare products; a persuasive campaign can alter perceived differentiation. Neither effect alone establishes a net gain. Include the campaign’s relevant economic cost before deciding whether a demand change raises profit or welfare.

Check Revenue Before Expanding to Minimum ATC

A lower average cost at a larger output does not establish a profitable expansion. Selling more along the given downward-sloping demand curve requires a lower price, which can also reduce revenue from earlier units. At the stated profit maximum, a feasible expansion cannot improve profit; in the ordinary graph, marginal cost exceeds marginal revenue beyond the chosen output. Compare the complete revenue and cost changes instead of multiplying the old price by the extra units.

Compare the Two Long-Run Models

Both models reach zero economic profit, but only perfect competition has P=MC=min ATC. Monopolistic competition has P=ATC>MC and output below minimum ATC.

Read quantity from the profit-maximizing MR–MC intersection, then move to the demand curve to read the price at that quantity. Compare that price with ATC at the same quantity for economic profit. Locate the separate minimum of ATC for the excess-capacity comparison. A tangency at one quantity does not make demand, MR, MC and ATC identical curves.

Report Three Different Comparisons

Finish a graph question with three separate statements: the profit comparison uses price versus ATC; the markup comparison uses price versus MC; the capacity comparison uses the two output quantities. Zero economic profit includes a normal return to resources through their opportunity costs. It does not mean the owner receives no compensation or that accounting profit must be zero.

Check the Model’s Definition and Limits

OpenStax’s monopolistic-competition lesson explains long-run entry and exit, the distinction between economic and accounting profit, production below minimum average cost and the benefits of variety. The following numerical model is an original illustration of those separate comparisons, not a real firm’s price or capacity estimate.

Read a Complete Numerical Example

In an invented smooth model, a firm chooses 12 units per day. At that output, price and ATC are both $17, MC is $8, and MR equals MC. Minimum ATC is $14 at 24 units per day. If the firm expands to 24, its given demand curve permits only an $8 price for every unit. Find economic profit at the chosen output, the price–MC gap, the excess-capacity quantity and profit at the larger output.

Try Three Capacity-and-Profit Questions

Connect Marginal and Average Comparisons

Review why marginal choices require a consistent cost comparison, distinguish input-demand changes from production scale changes, and continue through the CLEP Microeconomics learning hub.