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ECONOMICS • MARKET STRUCTURE

Monopoly, Competition & Deadweight Loss

Compare the competitive benchmark with monopoly pricing, output, markup, profit and the deadweight loss created by restricting quantity.

● MARKET POWERP = MC ↔ MR = MC
Monopoly price
Monopoly quantity
Operating profit
Deadweight loss

Reasoning inspector

live model state
Monopoly quantity—
Monopoly price—
Competitive quantity—
Competitive price—
Profit—
Deadweight loss—
Markup—

Experiment with the mechanism

With linear demand and constant marginal cost, a competitive benchmark expands output until price equals marginal cost. A monopolist instead chooses the quantity where marginal revenue equals marginal cost, raising price and leaving some mutually beneficial trades unrealized.

LEARN WITH THE SIMULATION

Understand Monopoly, Competition & Deadweight Loss by experimenting.

START HERE

A monopolist facing downward-sloping demand recognizes that selling an additional unit usually requires lowering price. Marginal revenue therefore lies below demand. In the simplified linear model, monopoly output is chosen where marginal revenue equals marginal cost, while the competitive benchmark expands output until price equals marginal cost. The difference creates a markup and can leave mutually beneficial trades unrealized.

BUILD THE IDEA

What you should understand first

  • Compare the monopoly condition MR = MC with the competitive condition P = MC.
  • Identify how monopoly restriction raises price and lowers quantity.
  • Interpret deadweight loss as gains from trade that disappear when output is restricted.

TRY IT YOURSELF

How does a higher marginal cost change monopoly markup and deadweight loss?

  1. Record the default monopoly and competitive outcomes.
  2. Raise marginal cost while keeping demand unchanged.
  3. Compare monopoly quantity, competitive quantity, markup, profit and deadweight loss.
  4. Try several marginal-cost values and identify which measures move together.
Read the visual:

Higher marginal cost lowers both monopoly and competitive quantity. The exact effects on markup, profit and deadweight loss depend on the demand geometry, so the inspector is more informative than assuming all measures move in the same proportion.

WHY IT WORKS 01

Why marginal revenue lies below demand

With downward-sloping demand, selling another unit requires a lower price. The monopolist gains revenue from the extra unit but also receives the lower price on units that would otherwise have sold for more. Marginal revenue therefore falls faster than the demand curve. The profit-maximizing monopoly quantity occurs where this marginal revenue equals marginal cost.

WHY IT WORKS 02

Deadweight loss comes from missing trades

Between the monopoly quantity and the competitive quantity, buyers are willing to pay more than the marginal cost of producing additional units. Those trades would increase total surplus, but they are not made because expanding output would reduce the monopolist’s profit under a single-price strategy. The resulting triangular welfare loss is distinct from the surplus transferred through the higher monopoly price.

DO NOT MIX THESE UP

Common misconception

Monopoly profit and deadweight loss are not the same thing. A transfer from consumers to the monopolist can raise producer surplus without itself being a social loss; deadweight loss comes from trades that no longer occur even though buyers’ willingness to pay exceeds marginal production cost.

PRACTICE CHALLENGE

Can monopoly profit fall while deadweight loss remains positive?

  • Choose a positive fixed cost and record monopoly profit and deadweight loss.
  • Raise fixed cost while leaving demand and marginal cost unchanged.
  • Observe what changes and what does not.
  • Explain why fixed cost affects accounting profit but not the output decision in this constant-marginal-cost model.
Reveal the reasoning

Yes. Fixed cost lowers profit dollar for dollar, but it does not change marginal revenue or marginal cost, so the monopoly quantity, monopoly price, markup, and deadweight loss remain unchanged in this simplified model. Profit can therefore fall or even become negative while the welfare loss from restricted output is still positive.

MODEL BOUNDARIES

What this simulation assumes

Every simulation simplifies reality or a mathematical system. These are the assumptions and limits to keep in mind while interpreting the results.

Model assumptions

  • Demand is linear and marginal cost is constant.
  • The monopolist charges a single price and chooses output where marginal revenue equals marginal cost.
  • The competitive benchmark is represented by price equal to marginal cost.

Model limitations

  • Strategic interaction, product differentiation, capacity limits, regulation, price discrimination and dynamic entry are omitted.
  • Fixed cost affects profit but not the output decision in this constant-marginal-cost setup.

CONNECT IT

Where this matters

  • Industrial organization
  • Market-power analysis
  • Competition policy education
  • Markup and welfare reasoning

WORDS THAT MATTER

Key vocabulary

Marginal revenue
The additional revenue from selling one more unit, accounting for the price effect along demand.
Markup
The difference between monopoly price and marginal cost in this model.
Deadweight loss
Lost total surplus from mutually beneficial trades that do not occur.
Competitive benchmark
The model outcome where price equals marginal cost.