Monopoly vs Monopolistic Competition
Monopoly and Monopolistic Competition are two Market Structures concepts in AP Economics that students often mix up. A monopoly is a market structure with a single seller producing a unique product with no close substitutes and significant barriers to entry. Monopolistic competition is a market structure with many firms selling differentiated products and facing low barriers to entry. Here is how they compare side by side.
A monopolist is the sole provider of a good or service and faces the entire market demand curve, allowing it to set price above marginal cost. Because of high barriers to entry, other firms cannot enter the market to compete.
Firms in monopolistic competition have some pricing power due to product differentiation but face competition from many rivals. In the long run, they earn zero economic profit as new firms enter when profits are positive.
Monopoly vs Monopolistic Competition: Similar Diagram, Opposite Long Run
| Monopoly | Monopolistic competition | |
|---|---|---|
| Number of firms | One | Many |
| Barriers to entry | High | Low |
| Product | Unique, no close substitutes | Differentiated, with many close substitutes |
| Demand facing the firm | Downward sloping and relatively inelastic | Downward sloping and relatively elastic |
| Short-run outcome | Can earn economic profit | Can earn economic profit |
| Long-run economic profit | Persists, protected by barriers | Zero, competed away by entry |
| Long-run price vs ATC | Price above ATC | Price equals ATC, at the tangency |
| Excess capacity | Not a general result. The monopolist may produce above or below the minimum-ATC output | Yes, and it persists in equilibrium |
The short-run diagrams look almost identical
Both firms face a downward-sloping demand curve, both therefore have marginal revenue below demand, and both find quantity where MR equals MC and then read price UP on the demand curve. Neither is a price taker. If you are shown a single short-run diagram with economic profit, you often cannot tell which structure it is from the picture alone. The difference is not in the geometry, it is in what happens next, and questions are frequently built to test exactly that.
Entry is the whole difference
Monopolistic competition has low barriers, so short-run economic profit attracts new firms. Each entrant takes some demand from the incumbents, shifting every existing firm's demand curve left and making it more elastic, and this continues until economic profit reaches zero. At that point the demand curve is tangent to average total cost: price equals ATC, and the firm produces on the downward-sloping part of ATC rather than at its minimum. That gap between the actual output and minimum-ATC output is excess capacity. A monopoly's barriers prevent this entirely, so its economic profit survives indefinitely.
Both are inefficient, in the same way and to different degrees
Both produce where price exceeds marginal cost, which means allocative inefficiency: there are units buyers value above what they cost to produce that do not get made, and that shortfall is deadweight loss. Both also fail productive efficiency, since neither produces at minimum ATC. The monopoly's markup is usually larger because it faces less elastic demand, having no close substitutes. It is worth being careful in an evaluation answer: monopolistic competition's inefficiency buys product variety, which has real value to consumers, so calling it simply wasteful overstates the case. See /sandbox/monopolistic-competition and /sandbox/monopoly.
Frequently asked questions
What is the difference between monopoly and monopolistic competition?
A monopoly is one firm protected by high barriers to entry, so its economic profit persists. Monopolistic competition has many firms selling differentiated products with low barriers, so entry competes economic profit away to zero in the long run. Their short-run diagrams look very similar; the long run is what separates them.
Why do monopolistically competitive firms earn zero profit in the long run?
Because barriers to entry are low. Short-run economic profit attracts new firms, which take demand from existing ones, shifting each incumbent's demand curve left until it is just tangent to average total cost. At that point price equals ATC and economic profit is zero, though the firm still earns a normal profit.
What is excess capacity?
Producing at a quantity below the one that minimises average total cost. Because a monopolistically competitive firm's demand curve is tangent to ATC on its downward-sloping section, the firm never reaches minimum ATC even in long-run equilibrium. It is the efficiency cost of having many differentiated sellers rather than a few large ones.
Live Monopoly graph. Drag the curves, or open the full version.
Live Monopolistic Competition graph. Drag the curves, or open the full version.
Related comparisons
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