Monopolistic Competition & Excess Capacity

You’ll be able to

State the defining features of monopolistic competition
Explain the long-run zero-profit outcome and why it is not efficient
Explain what excess capacity means and why it arises

Many firms, differentiated products, free entry

Monopolistic competition has many sellers, differentiated products, and free entry. Differentiation gives each firm a downward-sloping demand curve, so it has some price-setting power — unlike perfect competition. Free entry means economic profit is competed away in the long run — like perfect competition. The result combines features of both, which is exactly why it is a separate model rather than a special case of either.

The long-run outcome

Positive economic profit attracts entry. New entrants take customers, so each incumbent's demand curve shifts left and becomes more elastic — more substitutes exist. Entry continues until the demand curve is just tangent to ATC, meaning price equals average total cost and economic profit is zero. That tangency is the defining geometry of long-run monopolistic competition.

The long-run condition

P = ATC (zero profit, from free entry) but P > MC (from downward-sloping demand) and ATC is NOT at its minimum

Compare perfect competition, where P = MC = minimum ATC. Monopolistic competition achieves zero profit without achieving either efficiency.

Excess capacity

Because the tangency between a downward-sloping demand curve and a U-shaped ATC occurs on ATC's falling portion, the firm produces less than the output that would minimize average cost. The gap between them is excess capacity — the firm could produce more cheaply per unit if it produced more, and it does not. So productive efficiency fails, and P > MC means allocative efficiency fails too.

Is the differentiation worth it?

The efficiency losses are real, but so is the benefit: consumers get variety, and variety has value. The honest assessment is that monopolistic competition trades some productive and allocative efficiency for product diversity, and there is no clean way to say whether the trade is worth it. A strong free-response answer states the trade rather than condemning the market structure.

Worked example

A restaurant in a city of many restaurants earns positive economic profit. Trace the long-run adjustment and describe the final position.

1.Positive profit attracts new restaurants to enter the market.
2.Each existing restaurant loses some customers, so its demand curve shifts left.
3.More alternatives make each demand curve more elastic — flatter.
4.Entry stops when demand is tangent to ATC: P = ATC, zero economic profit.
5.At that tangency, output is below minimum-ATC output and P exceeds MC.

Answer: The restaurant ends with zero economic profit, producing below the output that would minimize its average cost — excess capacity — and charging above marginal cost. Neither efficiency condition holds, and consumers get variety in exchange.

Watch out

In long-run monopolistic competition, demand is tangent to ATC, not crossing it. Tangency is what makes profit exactly zero: a crossing would mean a range of profitable outputs, which entry would have eliminated.

Checkpoint

In long-run equilibrium, a monopolistically competitive firm has:

Checkpoint

Excess capacity in monopolistic competition means the firm:

Checkpoint

As new firms enter a monopolistically competitive market, an existing firm's demand curve:

On the exam

Draw the long-run graph with demand tangent to ATC and mark both the actual output and minimum-ATC output. Excess capacity is the horizontal gap between them, and questions ask you to identify it on the diagram.

Answer the 3 checkpoints as you read.