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Fundamentals of Business Economics and Management · Forms of Market

Monopolistic Competition: Features, Equilibrium and Excess Capacity

Updated 10 October 2026 · Fact-checked

Monopolistic competition is a market with many sellers offering differentiated but close substitute products, with free entry and exit. Each firm has some price control, so its demand curve slopes down. Firms earn abnormal profit in the short run, only normal profit in the long run, and operate with excess capacity.

Understand Monopolistic Competition

Think of toothpaste, soaps, biscuits or restaurants. Many sellers compete, yet each brand is a little different. That mix of competition and a small amount of monopoly power is monopolistic competition.

The main features are:
- Many sellers, each with a small share of the market.
- Product differentiation: products are close substitutes but not identical. The difference may be in quality, brand, packaging, location or service.
- Free entry and exit of firms in the long run.
- Selling costs: money spent on advertising and promotion to create or increase demand for a brand.
- Downward-sloping, fairly elastic demand curve, because each brand has loyal buyers but many substitutes exist.

Because the product is differentiated, the firm is a price maker within limits. If it raises price a lot, buyers move to rival brands. That is why demand is elastic but not perfectly elastic as in perfect competition.

Short-run equilibrium: The firm maximises profit where MC = MR, with MC cutting MR from below. Price is read from the demand (AR) curve at that output. If price is above average cost, the firm earns abnormal profit. If price is below average cost, it makes a loss.

Long-run equilibrium: Abnormal profit attracts new firms. Their substitutes take away part of each firm's demand, so each firm's demand curve shifts left. This continues until price equals average cost, so only normal profit remains. The AR curve is then tangent to the LAC curve. Losses work in reverse: firms leave and demand for the remaining firms rises.

Excess capacity: At the tangency point the LAC curve is still sloping downward. So the firm produces less than the output at the minimum of LAC. The gap between this output and the minimum-cost output is excess capacity. Price is also above marginal cost (P > MC), unlike perfect competition.

Key formulas to remember

Profit-maximising condition
MR = MC, with MC cutting MR from below
Applies in both short run and long run. Read price from the AR (demand) curve at this output.
Long-run equilibrium
P = AR = LAC (tangency), so profit is normal
Also MR = MC at the same output. The AR curve touches LAC on its falling part.
Price and marginal cost
P > MC in equilibrium
Because the demand curve slopes down, MR lies below AR. In perfect competition P = MC.
Excess capacity
Excess capacity = output at minimum LAC − actual equilibrium output
Arises because the tangency lies on the downward-sloping part of LAC.
Abnormal profit
(AR − AC) × Output
Positive in the short run if price exceeds average cost; zero in long-run equilibrium.

How to solve Monopolistic Competition questions

Use this method for any question on monopolistic competition, whether it asks for features, differences, equilibrium or excess capacity.

  1. 1Identify the keyword: differentiated product, selling cost, abnormal profit, normal profit, tangency or excess capacity.
  2. 2Recall the base features: many sellers, differentiated products, free entry and exit, selling costs.
  3. 3Decide whether the question is about the short run or the long run.
  4. 4For short run, apply MR = MC and compare price (AR) with AC to find profit or loss.
  5. 5For long run, apply free entry and exit: abnormal profit means entry, loss means exit, ending with P = AC.
  6. 6For capacity questions, remember tangency on the falling part of LAC, so output is below the minimum-cost output.
  7. 7For comparison questions, check price control, product type, demand elasticity, P versus MC and efficiency.
  8. 8Eliminate options that use words like perfectly elastic, identical product or barriers to entry.

Quickest way: Keyword matching for MCQs

When to use it: Use this for theory MCQs where you have under a minute per question.

  1. If the option says 'identical products' or 'perfectly elastic demand', it is perfect competition. Reject it.
  2. If it says 'barriers to entry' or 'single seller', it is monopoly. Reject it.
  3. If it says 'few sellers' or 'interdependence', it is oligopoly. Reject it.
  4. If it mentions brands, advertising or selling costs with many sellers, choose monopolistic competition.
  5. For long-run questions, pick 'normal profit' and 'excess capacity'.
  6. For numbers, compute (AR − AC) × output for profit, or total cost ÷ output for average cost.

Common mistakes in Monopolistic Competition

  • Saying the firm earns abnormal profit in the long run.

    Students remember the short-run diagram and forget free entry.

    Fix: Link entry to profit. Abnormal profit invites new firms until price equals average cost and only normal profit is left.

  • Treating the demand curve as perfectly elastic.

    Confusing it with perfect competition because both have many sellers.

    Fix: Product differentiation gives some price control. The demand curve slopes down and is fairly elastic.

  • Calling selling costs the same as production costs.

    Both are expenses of the firm.

    Fix: Selling costs are spent to change the demand for the product, such as advertising. Production costs are spent to make the product.

  • Thinking excess capacity means unsold stock or idle machines.

    The word 'excess' sounds like waste in the factory.

    Fix: It means the firm produces less than the output at which average cost is lowest. It is a gap between two output levels.

  • Writing P = MC for monopolistic competition.

    Copying the perfect competition result.

    Fix: Here MR is below AR, so MR = MC gives P > MC.

  • Calling a firm in monopolistic competition a price taker.

    Many sellers suggests perfect competition.

    Fix: Each firm has a distinct brand and so has limited power over price. It is a price maker within limits.

Worked examples

Example 1

A firm in monopolistic competition sells 200 units at ₹50 per unit. Its average cost at this output is ₹42. Calculate its abnormal profit and say what happens in the long run.

Show the solution
  1. Profit per unit = AR − AC = ₹50 − ₹42 = ₹8.
  2. Total abnormal profit = ₹8 × 200 = ₹1,600.
  3. Because entry is free, abnormal profit attracts new firms.
  4. New firms offer close substitutes, so this firm's demand curve shifts left.
  5. This continues until price equals average cost and profit becomes normal.

Answer: Abnormal profit is ₹1,600. In the long run new firms enter and profit falls to normal, with price equal to average cost.

Example 2

Which statement correctly describes long-run equilibrium of a firm in monopolistic competition? (A) Price equals marginal cost and output is at minimum average cost. (B) Price equals average cost and the firm has excess capacity. (C) Firm earns abnormal profit due to barriers to entry. (D) Demand curve is perfectly elastic.

Show the solution
  1. Option A describes perfect competition, where P = MC and output is at minimum LAC. Reject it.
  2. Option C is wrong because entry is free, so abnormal profit disappears.
  3. Option D is wrong because differentiation makes demand downward sloping.
  4. Option B is right: AR is tangent to LAC, so P = AC, and the tangency is on the falling part of LAC, giving excess capacity.

Answer: Option B

Exam tips

  • Expect direct theory MCQs on features. Learn the five features as a quick list.
  • Questions on difference from perfect competition usually test product type, demand curve, price control and efficiency.
  • Remember the pair 'normal profit and excess capacity' for long-run equilibrium.
  • Selling cost questions test purpose: they shift or increase demand and are not production costs.
  • Do not leave any question blank. There is no negative marking, so guess after eliminating options.

Practice questions from Forms of Market

Monopolistic Competition in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Monopolistic Competition: frequently asked questions

What are the main features of monopolistic competition?

There are many sellers, products are differentiated but close substitutes, entry and exit are free, and firms spend on selling costs. Each firm has some control over price, so its demand curve slopes downward.

What is the difference between perfect and monopolistic competition?

In perfect competition products are identical, the firm is a price taker and demand is perfectly elastic. In monopolistic competition products are differentiated, the firm has limited price control and demand slopes down. Also, P = MC in perfect competition but P > MC in monopolistic competition.

What is excess capacity in monopolistic competition?

It is the gap between the output at minimum long-run average cost and the lower output the firm actually produces in equilibrium. It arises because the demand curve is tangent to LAC on its falling part.

What are selling costs?

Selling costs are expenses such as advertising and sales promotion that aim to create or raise demand for a firm's brand. They differ from production costs, which are incurred to make the product.