What you'll learn
- What monopolistic competition means and why its assumptions matter.
- How firms set price and output in the short run and long run.
- Why product differentiation, branding and advertising are central to this market structure.
- How to evaluate monopolistically competitive markets using allocative and productive efficiency.
Starting point: what kind of market is this?
A market structure is the set of conditions in a market, including the number of firms, the ease of entry, the type of product sold, and how much power firms have over price.
Monopolistic competition sits between perfect competition and monopoly. There are many firms, so no single firm dominates the market. But unlike perfect competition, each firm sells a slightly different product, so it has some control over its price.
Typical examples include UK high-street coffee shops, hairdressers, takeaways, gyms, restaurants, estate agents and independent clothing brands.
Monopolistic competition
Monopolistic competition is a market structure with many firms, freedom of entry and exit, and differentiated products, giving each firm some price-setting power while still facing strong competition from close substitutes.
The key assumptions
1. There are many firms
There are enough firms that each one has only a small share of the market. One coffee shop cutting its price is unlikely to trigger a whole-market price war.
This means firms are usually independent in their decision-making, unlike oligopoly where firms are highly interdependent.
2. Products are differentiated
Product differentiation means firms make their products appear different from rivals’ products. The difference might be real, such as better quality ingredients, or perceived, such as branding and packaging.
Differentiation can happen through:
- quality
- design
- customer service
- location
- branding
- convenience
- online reviews
- advertising
This is why non-price competition matters so much.
Why differentiation matters
Product differentiation gives each firm a downward-sloping demand curve because some customers are loyal enough to keep buying even if the firm raises price slightly.
3. There is freedom of entry and exit
Barriers to entry are obstacles that make it difficult for new firms to enter a market. In monopolistic competition, these barriers are assumed to be low.
If existing firms make abnormal profit, new firms can enter. If firms make losses, some leave.
4. Firms aim to maximise profit
A firm is assumed to choose the output where marginal revenue equals marginal cost.
MR and MC
Marginal revenue is the extra revenue from selling one more unit. Marginal cost is the extra cost of producing one more unit. Profit is maximised where MR=MCMR = MCMR=MC, provided marginal cost is rising.
Classifying a local coffee-shop market
Suppose a town has several independent cafés, a Costa, a Starbucks and a few bakery-cafés.
- The market has many sellers, so no single café is likely to control total town demand.
- The products are differentiated: one café may compete on atmosphere, another on speed, another on premium coffee or loyalty apps.
- Entry is possible because a new café can rent premises and buy equipment, although strong locations and brand reputation may still be difficult to copy.
- The best classification is monopolistic competition because firms face close substitutes but still have some price-setting power.
Calling every branded market a monopoly
A firm having a brand does not automatically make it a monopoly. In monopolistic competition, firms have some market power, but customers still have many close alternatives.
Demand and revenue for the firm
In monopolistic competition, the firm’s average revenue curve is also its demand curve. Average revenue means revenue per unit sold, which is the same as price.
Because the firm’s product is differentiated, demand slopes downwards. To sell more, the firm normally has to reduce price.
Its marginal revenue curve lies below average revenue. This is because lowering price to sell an extra unit often means accepting a lower price on other units too.
Price comes from AR
On a monopolistic competition diagram, find output using MR=MCMR = MCMR=MC, then go up to the AR curve to find price. Do not take price from the MR curve.
Short-run equilibrium
The short run is the period in which the number of firms in the market is fixed. A firm may make abnormal profit, normal profit, or a loss.
Normal and abnormal profit
Normal profit is the minimum profit needed to keep a firm in its current use, and it is included in costs. Abnormal profit is profit above normal profit.
In the short run, a monopolistically competitive firm:
- chooses output where MR=MCMR = MCMR=MC
- charges the price consumers are willing to pay on the AR curve
- may earn abnormal profit if price is above average cost
The diagram below shows short-run abnormal profit and long-run normal profit for a monopolistically competitive firm.
Calculating short-run abnormal profit
A takeaway maximises profit by selling 200 meals per day. At this output, the price from the demand curve is £8 per meal and average cost is £6.50 per meal.
- The firm uses the profit-maximising rule, so it produces 200 meals where MR=MCMR = MCMR=MC.
- Price is read from the AR curve, so the firm charges £8 per meal.
- Average profit per meal is £8 minus £6.50, giving £1.50.
- Total abnormal profit is £1.50 multiplied by 200 meals, giving £300 per day.
The profit formula behind this is:
Abnormal profit=(AR−AC)×Q\text{Abnormal profit} = (AR - AC) \times QAbnormal profit=(AR−AC)×QHow the short run adjusts to the long run
The long run is the period in which all factors of production are variable and firms can enter or leave the market.
If firms are making abnormal profit, new firms enter. This increases the number of substitutes available to consumers. As a result, demand for each existing firm falls.
For an individual firm, its AR curve shifts left. Demand may also become more price elastic because consumers have more alternatives.
This process continues until abnormal profit is competed away. In long-run equilibrium, the firm earns normal profit.
Long-run adjustment
In monopolistic competition, freedom of entry means abnormal profit attracts new firms, reducing each firm’s demand until only normal profit remains in the long run.
Tracing entry into the market
A popular gym in a town is making abnormal profit because it has strong demand and high membership prices.
- Abnormal profit signals an opportunity, so new gyms, personal trainers and boutique fitness studios enter the local market.
- Consumers now have more substitutes, so the original gym’s demand curve shifts left.
- The gym may reduce price, improve facilities or increase advertising, but its abnormal profit falls as customers spread across more providers.
- Long-run equilibrium is reached when price equals average cost, so the gym earns normal profit.
Long-run normal profit is a model result
In the real world, some firms may keep abnormal profit for longer if they have strong brand loyalty, a unique location, patents, excellent reviews, or access to digital platforms that rivals cannot easily copy.
Non-price competition and advertising
Non-price competition means competing through methods other than lowering price. This is central to monopolistic competition because firms want to make demand less price elastic and build customer loyalty.
Examples include:
- advertising and social media campaigns
- loyalty schemes
- better customer service
- unique packaging
- faster delivery
- product variety
- ethical or local sourcing
Advertising can be informative, helping consumers compare products. It can also be persuasive, making products appear more different than they really are.
Using advertising to shift demand
A local restaurant starts advertising its locally sourced ingredients and improves its online booking system.
- The restaurant becomes more visible and more differentiated from close rivals.
- Some consumers become less willing to switch to substitutes, so demand for this restaurant may become less price elastic.
- If the advertising is successful, the firm’s AR curve shifts right, allowing a higher price and output in the short run.
- If rivals copy the strategy or increase their own advertising, the gain may be reduced in the long run.
Ignoring non-price competition
Do not write as if monopolistically competitive firms only compete by changing price. Differentiation, branding, location and advertising are often more important.
Efficiency in monopolistic competition
Economists judge market outcomes using different types of efficiency.
Allocative efficiency
Allocative efficiency occurs when resources are distributed according to consumer preferences. In a market diagram, it occurs where P=MCP = MCP=MC.
Productive efficiency
Productive efficiency occurs when a firm produces at the lowest point on its average cost curve, meaning it produces at minimum average cost.
Allocative efficiency
In long-run monopolistic competition, price is usually greater than marginal cost. This means the value consumers place on the last unit is greater than the cost of producing it.
So the market underproduces compared with the allocatively efficient level.
In short: monopolistically competitive markets are usually allocatively inefficient.
Productive efficiency
In the long run, the firm does not usually produce at the minimum point of average cost. It produces at a lower output than the minimum efficient scale.
This gap is called excess capacity.
Excess capacity
Excess capacity occurs when a firm produces below the output where average cost is minimised, so it has unused potential to produce at a lower average cost.
This means monopolistically competitive firms are usually productively inefficient.
Judging efficiency from a long-run diagram
A monopolistically competitive firm is in long-run equilibrium at output Q2. At this output, price is £12, marginal cost is £8, and the minimum average cost occurs at a higher output.
- Allocative efficiency requires P=MCP = MCP=MC, but here price is £12 and marginal cost is £8.
- Since P>MCP > MCP>MC, consumers value extra output more than it costs to produce, so the firm is underproducing from society’s viewpoint.
- Productive efficiency requires output at minimum average cost, but the firm is producing below that level.
- The market is both allocatively inefficient and productively inefficient, although consumers may still benefit from variety and choice.
Evaluation: is monopolistic competition “bad”?
It is not enough to say “inefficient, therefore bad”. A strong evaluation weighs costs against benefits.
Arguments against monopolistic competition
- Prices are higher than marginal cost, so there is allocative inefficiency.
- Firms do not produce at minimum average cost, so there is productive inefficiency.
- Advertising may be wasteful if it only persuades consumers rather than providing useful information.
- Small firms may miss out on economies of scale, keeping costs higher.
Arguments in favour
- Consumers benefit from choice, variety and convenience.
- Product differentiation can encourage innovation and better quality.
- Advertising can provide information and reduce search costs.
- Low barriers to entry can keep firms responsive to consumer preferences.
- In local services, spare capacity may be useful because customers value short queues, flexible bookings and convenience.
Balanced judgement
Monopolistic competition is usually statically inefficient, but it may still improve consumer welfare through variety, innovation, convenience and non-price competition.
Linking it to essays
For AO1, define the structure and explain the assumptions clearly.
For AO2, apply it to realistic markets such as cafés, gyms, restaurants, hairdressers or app-based takeaway services in the UK. Avoid using natural monopolies or oligopolies unless you are explicitly comparing structures.
For AO3, use the diagram: MR=MCMR = MCMR=MC sets output, AR sets price, and free entry removes abnormal profit in the long run.
For AO4, evaluate whether the assumptions hold in reality. Strong brands, prime locations, online reviews and customer loyalty can create barriers that allow abnormal profit to persist.
In the exam
- Define monopolistic competition using three features: many firms, differentiated products, and low barriers to entry.
- For diagrams, always show AR, MR, AC and MC; set output where MR=MCMR = MCMR=MC and read price from AR.
- Evaluate efficiency carefully: mention P>MCP > MCP>MC for allocative inefficiency, excess capacity for productive inefficiency, then balance this against choice, variety and innovation.
Check yourself
- Why does product differentiation give a firm a downward-sloping demand curve?
- How does abnormal profit in the short run lead to normal profit in the long run?
- Why is a monopolistically competitive firm usually not productively efficient in the long run?
