Short-Run Price and Output in Monopolistic Competition
A differentiated seller chooses output before reading price from demand. In the standard short-run model, compare feasible profit outcomes, check whether operating beats shutting down, and distinguish markup from profit. Work through the examples and try three original questions.
Differentiation gives each firm a downward-sloping demand curve.
Check Three Differentiated-Seller Cases
Use a single-price differentiated seller with known demand and costs, feasible nonnegative output, and no unstated capacity constraints. MR=MC identifies a candidate positive output in a smooth interior model; it must maximize profit among feasible choices. Compare the best operating choice with zero output as well. Unavoidable fixed costs remain payable during a short-run shutdown.
A monopolistically competitive firm’s markup exists because
- downward-sloping demand permits price above marginal cost
- entry barriers protect permanent economic profit
- the firm faces perfectly elastic demand
- a regulator sets price above marginal cost
- average total cost is constant at every output
downward-sloping demand permits price above marginal cost In the standard smooth model at the profit-maximizing positive interior output, MR=MC and downward-sloping demand places price above MR. This markup does not establish that price covers ATC.
Advertising by a monopolistically competitive firm can be socially useful when it
- guarantees higher economic profit forever
- eliminates product differentiation
- reduces consumer information
- forces every rival to exit
- provides information that helps buyers compare products
provides information that helps buyers compare products Informative advertising can lower search costs and help consumers match products to preferences, although persuasive advertising may also create costs.
A differentiated seller’s best feasible positive output is 80 units, where MR equals MC. Demand gives a price of $14 and average variable cost is $8 there. Fixed costs are unavoidable during this period, with no other avoidable costs. What is the short-run choice?
- Produce 80 units and charge $14
- Produce where price equals marginal cost
- Charge the marginal-revenue value
- Produce at minimum average total cost
- Exit regardless of average cost
Produce 80 units and charge $14 The stated best positive choice sells 80 units at $14. Revenue exceeds variable cost by ($14 − $8) × 80 = $480, so operating contributes $480 toward the same unavoidable fixed costs that would remain during shutdown. ATC is still needed to measure economic profit; charging the MR value would misread demand.
Video Lesson: A Differentiated Firm’s Short-Run Choice
A focused video lesson from Khan Academy.
Check the Candidate Output
For a smooth interior operating choice, find candidate outputs where MR equals MC, compare feasible profit outcomes, and read the chosen price from demand. The firm can earn profit, break even or incur a loss. A marginal equality alone does not establish a global maximum or show that operating beats shutting down.
Read Price from Demand
The differentiated seller uses the same output-and-price logic as a single-price monopoly because its own demand slopes downward. At the selected positive output q, move up to demand to read price and compare that price with ATC at the same quantity. The presence of many sellers does not make each differentiated seller a price taker.
Compare Operating with Shutdown
At a positive output, economic profit is (P − ATC) × Q. To decide whether to operate, compare the best feasible revenue minus avoidable operating costs with zero output. With all fixed costs unavoidable and variable cost as the only avoidable cost, operating beats shutdown when that contribution is positive; equality gives a tie. A loss-making firm can therefore keep operating in the short run. Do not infer shutdown from P below ATC alone.
Identify the Differentiation
Product differentiation can involve physical features, quality, service, location, atmosphere or perceived differences. Close substitutes limit pricing freedom. Their presence can make buyers more price-sensitive, but comparing the elasticity of two firms requires their actual demand conditions; the market label alone does not supply a numerical elasticity.
Trace the Seller’s Own Demand
A restaurant illustrates the mechanism: after a price increase, some customers stay because of location or preferences while others switch to alternatives. This response concerns the restaurant’s own demand. It does not require treating every differentiated meal as one homogeneous product.
Calculate the Salon’s Economic Profit
Suppose 80 appointments is a salon’s profit-maximizing feasible short-run output, MR=MC there, demand gives a price of $45 and economic ATC is $38. Its economic profit is (45-38)80=$560. Price comes from demand, not MR. Feasible entry by close substitutes can change future demand; the calculation does not establish permanent profit.
Count Advertising Costs Once
For an extra $1,000 advertising campaign, compare added revenue with added production costs, other added costs and the $1,000 campaign cost. Equivalently, the extra operating contribution before paying for the campaign must exceed $1,000 to increase profit. If a figure already measures profit after advertising cost, do not subtract the campaign cost again. A sales increase alone is insufficient.
Separate Markup from Profit
Markup does not guarantee profit. A firm can have P>MC but P<ATC because fixed cost or weak demand produces a loss. Allocative markup and accounting of total cost are separate.
Distinguish Short Run from Entry
The short run assumes the number of firms fixed. If the question asks what occurs after profit attracts entry, shift to the long-run tangency analysis rather than leaving the initial demand curve unchanged.
Recheck Demand and Cost Changes
A successful advertisement, a new feature or a rival’s exit can change the firm’s demand and MR. An input-price change shifts MC when it changes marginal production cost; a change affecting only fixed cost need not shift MC. Recompute feasible profit outcomes and the shutdown comparison using the stated changes.
Separate Private Profit and Information Benefits
Informative advertising can help buyers compare products and reduce search costs. Loyalty-building advertising may reduce price sensitivity, while comparison information may increase it. A privately profitable campaign is not automatically a net social benefit: evaluate the information supplied, resource cost and stated effects separately.
Use Four Separate Comparisons
Check four different quantities: MR and MC help select an interior operating candidate; demand gives its price; ATC determines economic profit; avoidable costs determine whether operating improves on shutdown. Keep these comparisons separate when reading the graph.
Check the Output-and-Cost Definitions
OpenStax’s monopolistic-competition lesson explains differentiated sellers and advertising. Its monopoly output-and-price lesson separates the output choice from reading price on demand. The short-run cost discussion explains why unavoidable fixed costs remain during shutdown; its price-taking market assumption is different from the differentiated-seller model here.
Work a Consistent Short-Run Example
An invented seller has demand P = 44 − Q, variable cost VC = 8Q + 0.5Q² and $240 of unavoidable fixed cost for the period. Consider feasible output from 0 to 44 units. Find its best operating quantity, price, economic profit and shutdown comparison. These are hypothetical model values, not a business forecast.
Check your reasoning
Revenue is 44Q − Q², so contribution before fixed cost is 36Q − 1.5Q² = 216 − 1.5(Q − 12)². This expression is largest at Q = 12. There MR = 44 − 2Q = $20 and MC = 8 + Q = $20, while price on demand is $32.
At 12 units, revenue is $384 and variable cost is $168, so AVC is $14. Total cost is $408 and ATC is $34. Economic profit is $384 − $408 = −$24. Shutdown leaves the unavoidable $240 fixed cost and no revenue, producing a $240 loss. Operating therefore improves the outcome by $216 even though price is below ATC.
The price–MC markup is $32 − $20 = $12 per unit. It is not economic profit per unit: price minus ATC is −$2. For a separate advertising decision, an extra $120 revenue with $90 of extra production cost and a $40 campaign cost changes profit by $120 − $90 − $40 = −$10. More sales alone do not justify that campaign.
Try Three Short-Run Decision Questions
Choose one answer, then check your reasoning. These are short learning checks, not an exam score. If the controls are unavailable, the explanations remain readable below each question.
Answer D. Operating revenue is $384 and total cost is $408, giving a $24 loss. Shutdown still incurs $240. Positive contribution of $216 makes the stated best operating choice preferable; a loss alone does not require shutdown.
Answer C. The change is $120 − $90 − $40 = −$10. Count each added cost once. The $30 contribution before advertising does not cover the $40 campaign.
Answer A. Markup is P − MC = $12 per unit. Economic profit is (P − ATC) × Q = ($32 − $34) × 12 = −$24. The two measures answer different questions.
Connect Short-Run Choice and Long-Run Entry
Reza is an experienced Math instructor and a test-prep expert who has been tutoring students since 2008. He has helped many students raise their standardized test scores--and attend the colleges of their dreams. He works with students individually and in group settings, he tutors both live and online Math courses and the Math portion of standardized tests. He provides an individualized custom learning plan and the personalized attention that makes a difference in how students view math.
Related to This Article
More math articles
- Student speech
- The Ultimate SAT Math Course (+FREE Worksheets & Tests)
- Dominant Culture, Subcultures, and Countercultures
- Disasters and Collective Response
- Getting a Math Degree: Hacks to Make Your Life Easier
- Understanding the Prompt and Rubric
- The Best Grade 3 ELA Practice Tests for Oklahoma Students
- 8th Grade PSSA Math Worksheets: FREE & Printable
- A wage change creates substitution and income effects in labor supply
- The Best Grade 4 ELA Practice Tests for California Students
What people say about "Short-Run Price and Output in Monopolistic Competition"?
No one replied yet.