Business Economics · Price Determination in Different Markets

Monopolistic Competition: CA Foundation Business Economics

Updated 1 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. Solve questions by setting MR = MC. In the long run, entry removes abnormal profit and price equals average cost.

Understand Monopolistic Competition

Monopolistic competition sits between perfect competition and monopoly. It has the large number of sellers and free entry of perfect competition. It also has the product differentiation that gives each seller a little monopoly power over its own brand.

Product differentiation means each firm's product differs from rivals' in quality, design, packaging, brand name, location or service. Examples are toothpaste, soaps, restaurants, clothing brands and tuition classes. The products are close substitutes, not identical. So buyers have a preference, but they will switch if the price gap becomes large.

Because of this, the firm faces a downward sloping demand curve. It is fairly elastic, since many substitutes exist. The firm is a price maker within limits. Its MR curve lies below the AR curve. The firm sells more only by cutting price or by spending on promotion.

Selling costs are expenses to change the demand for the product: advertising, sales promotion, free samples, salesmen and displays. They shift the demand curve to the right and make it less elastic. They are an important feature here, but they are not a cost of production. Under perfect competition they are absent, since the product is homogeneous. They matter most under monopolistic competition and oligopoly.

In the short run, the firm maximises profit where MR = MC, with MC cutting MR from below. Depending on where AR stands against AC at that output, it earns abnormal profit, normal profit or a loss. In the long run, free entry and exit adjust the number of firms. Abnormal profit attracts new firms, which shifts each firm's demand curve left. Losses push firms out, and demand shifts right. The process stops at normal profit, where AR = AC.

Key formulas to remember

Equilibrium condition: MR = MC, with MC cutting MR from below; Applies in both the short run and the long run. It fixes the profit-maximising output.
Short-run abnormal profit: AR > AC at equilibrium output; profit = (AR − AC) × Q; Profit is the area between the price and AC at that output.
Short-run loss: AR < AC at equilibrium output; loss = (AC − AR) × Q; The firm continues in the short run if AR ≥ AVC.
Long-run equilibrium: MR = MC and AR = AC (normal profit); The AR curve is tangent to the LAC curve at the output where MR = MC.
Excess capacity: Excess capacity = Output at minimum LAC − Actual long-run output; The tangency occurs on the falling part of LAC, so output is below the minimum-cost output.
Price–MC relation: P > MC in equilibrium; Unlike perfect competition, where P = MC.

How to solve Monopolistic Competition questions

Use this method for any MCQ, numerical or conceptual, on monopolistic competition.

1Identify the market: many sellers, differentiated products, free entry and exit, some price control. If the products are identical, it is not this market.
2Note whether the question is about the short run or the long run.
3For numbers, find the output where MR = MC. Check that MC is rising there.
4Compute price from the demand (AR) at that output, then compare it with AC.
5If AR > AC, the firm earns abnormal profit. If AR = AC, normal profit. If AR < AC, loss.
6For the long run, apply free entry: abnormal profit means entry and a left shift of demand. Loss means exit and a right shift. The end result is AR = AC.
7For concept questions, compare with perfect competition (P = MC, minimum AC) and monopoly (barriers to entry).
8Eliminate options that break these rules, then pick the best answer.

Quickest way: Rule-based elimination

When to use it: Use this for most theory MCQs, where two options are usually clearly wrong.

Remember the tag line: many sellers, differentiated product, free entry, selling costs.
Long run means normal profit. Eliminate any option that shows abnormal profit in the long run.
Long run also means excess capacity and P > MC. Eliminate options saying P = MC or minimum AC output.
Demand curve means downward sloping and elastic. Eliminate horizontal or perfectly inelastic.
In numerical questions, solve MR = MC first. Skip if it needs long algebra and you are unsure.

Common mistakes in Monopolistic Competition

Saying the firm earns abnormal profit in the long run.
Students copy the short-run diagram into the long run.
Fix: Free entry removes abnormal profit. Long run means AR = AC and normal profit.
Writing that price equals marginal cost in long-run equilibrium.
It is the perfect competition result and gets mixed up.
Fix: Here the AR curve slopes down, so MR is below AR. At MR = MC, price is above MC.
Treating selling costs as part of production cost.
Both are expenses of the firm.
Fix: Production costs make the product. Selling costs change demand. They shift the demand curve, not the cost of making each unit.
Saying the long-run tangency is at the lowest point of the LAC curve.
Students link normal profit to minimum cost, as in perfect competition.
Fix: The downward sloping AR is tangent to LAC on its falling part. So output is lower than the minimum-cost output. That gap is excess capacity.
Confusing product differentiation with a homogeneous product or with monopoly.
The term 'monopolistic' suggests a single seller.
Fix: There are many sellers. Each has a monopoly only over its own brand.

Worked examples

Example 1

In the long-run equilibrium of a firm under monopolistic competition, which statement is correct?
(a) Price is equal to marginal cost
(b) The firm earns abnormal profit
(c) Price equals average cost and is above marginal cost
(d) The firm produces at the minimum point of LAC

Show the solution

Long run: free entry and exit remove abnormal profit, so AR = AC. This rules out (b).
The AR curve slopes down, so MR < AR. At MR = MC, price is above MC. This rules out (a).
The tangency lies on the falling part of LAC, not at its minimum. This rules out (d).
Option (c) fits both conditions.

Answer: (c)

Example 2

A monopolistically competitive firm produces 200 units at the output where MR = MC. At this output, AR is ₹50 and AC is ₹42. What is its profit, and what will happen in the long run?
(a) ₹1,600; new firms enter
(b) ₹1,600; firms leave
(c) ₹10,000; new firms enter
(d) ₹8,400; firms leave

Show the solution

Profit per unit = AR − AC = 50 − 42 = ₹8.
Total profit = 8 × 200 = ₹1,600.
This is abnormal profit, since AR > AC.
Abnormal profit attracts new firms. Entry shifts each firm's demand left until AR = AC.

Answer: (a) ₹1,600; new firms enter

Example 3

Which of the following is a feature that distinguishes monopolistic competition from perfect competition?
(a) Large number of sellers
(b) Freedom of entry and exit
(c) Product differentiation
(d) Profit maximisation at MR = MC

Show the solution

Large number of sellers is common to both markets.
Free entry and exit is common to both.
Both types of firm maximise profit where MR = MC.
Only monopolistic competition has differentiated products. Perfect competition has homogeneous products.

Answer: (c) Product differentiation

Exam tips

Questions often ask for the difference from perfect competition or monopoly. Learn three points: product type, demand curve shape and P versus MC.
Expect direct statements on the long run: normal profit, excess capacity, P > MC. Learn them as a set.
Selling costs questions test the idea that they shift or reshape demand and are absent in perfect competition.
With 0.25 negative marking, attempt theory questions where you can eliminate two options. Skip a numerical question if you cannot find MR = MC quickly.

Practice questions from Price Determination in Different Markets

Monopolistic Competition: frequently asked questions

What are the main features of monopolistic competition?

There are many sellers, differentiated products that are close substitutes, free entry and exit, and some control over price. Selling costs such as advertising are common. The firm's demand curve slopes downward and is fairly elastic.

What is the difference between perfect competition and monopolistic competition?

Perfect competition has identical products and a horizontal demand curve, so firms are price takers. Monopolistic competition has differentiated products and a downward sloping demand curve, so firms have some price control. In the long run, perfect competition gives P = MC at minimum AC, but monopolistic competition gives P > MC and excess capacity.

What is excess capacity in monopolistic competition?

It is the gap between the output a firm produces in long-run equilibrium and the output at the minimum point of its LAC curve. It arises because the downward sloping demand curve touches LAC on its falling part. The firm could lower its unit cost by producing more, but it does not.

What are selling costs?

Selling costs are expenses to create or increase demand, such as advertising and sales promotion. They shift the demand curve right and can make it less elastic. They are different from production costs.