Monopolistic Competition

You’ll be able to

Describe the characteristics of monopolistic competition
Explain the short-run and long-run equilibria of a monopolistically competitive firm
Explain why these firms have excess capacity and are not allocatively efficient

Many firms, differentiated products

Monopolistic competition blends features of both extremes: many firms and easy entry and exit (like perfect competition), but differentiated products (like monopoly). Restaurants, salons, and clothing brands compete on quality, branding, and location, not just price. Because each firm’s product is slightly unique, each faces a downward-sloping demand curve and has some price-setting power — but the ease of entry and abundance of substitutes keep that power limited. Firms also engage in non-price competition through advertising and product differentiation.

Short-run profit, long-run break-even

Like a monopoly, a monopolistically competitive firm faces downward-sloping demand, so MR < P, and it maximizes profit at MR = MC, then sets price from demand. In the short run it can earn economic profit or loss. But because entry is easy, the long run mirrors perfect competition: profits attract entrants (shifting each firm’s demand left as customers spread out), and losses drive firms out, until each firm earns zero economic profit. In long-run equilibrium, the demand curve is tangent to the ATC curve at the profit-maximizing quantity.

Excess capacity and inefficiency

At the long-run tangency, the firm does not produce at minimum ATC (unlike perfect competition) — it produces on the downward-sloping portion of ATC, leaving excess capacity (it could lower average cost by producing more). And because demand slopes down, P > MC at the profit-maximizing output, so the market is allocatively inefficient with some deadweight loss. The trade-off society accepts is product variety: the inefficiency is the price paid for the diversity of differentiated goods consumers value.

Long-run equilibrium features

MR = MC (profit-max) · Zero economic profit (P = ATC, tangency) · P > MC (inefficient) · excess capacity

Like monopoly: downward-sloping demand, MR < P, P > MC. Like perfect competition: easy entry drives long-run profit to zero. Unlike perfect competition: not at minimum ATC.

Worked example

A monopolistically competitive coffee shop is earning short-run economic profit. Describe how the market adjusts to long-run equilibrium and what characterizes the firm there.

1.Short-run economic profit attracts new coffee shops because entry into the market is easy.
2.As rivals enter, they draw away some customers, shifting each existing firm’s demand curve left (and making it more elastic).
3.Entry continues until each firm’s demand curve is just tangent to its ATC curve, so economic profit falls to zero.
4.At that tangency the firm still prices where P > MC and produces below minimum ATC, leaving excess capacity.

Answer: Entry shifts each firm’s demand left until demand is tangent to ATC and economic profit is zero. The firm ends up with excess capacity (producing below minimum-ATC output) and P > MC — earning a normal profit but remaining allocatively inefficient.

Checkpoint

In long-run equilibrium, a monopolistically competitive firm differs from a perfectly competitive firm in that it:

Watch out

In the long run, monopolistic competition earns zero economic profit (like perfect competition) but does not reach minimum ATC — it leaves excess capacity and prices above MC. Do not treat its long-run outcome as fully efficient.

Checkpoint

Which feature do monopolistic competition and monopoly share, but perfect competition does not?

On the exam

For monopolistic competition, draw it like a "shrunken monopoly": downward-sloping demand with MR below it, MR = MC for quantity, and in the long run the demand curve tangent to ATC (zero profit). Label the excess capacity gap between that output and minimum ATC.

Answer the 2 checkpoints as you read.