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Market Structures

Perfect competition: equilibrium and efficiency

  • 3 things to know
  • Papers 1 and 3

Overview

Recall questions on short-run profits and losses, how entry and exit restore normal profit, and the efficiency of long-run equilibrium.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Key term

What level of profit do perfectly competitive firms earn in long-run equilibrium?

Key term

On a diagram showing short-run supernormal profit, how is the profit area represented?

Key term

What happens when perfectly competitive firms earn supernormal profits in the short run?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What happens when perfectly competitive firms earn supernormal profits in the short run?

    Model answer

    New firms are attracted to enter the market, increasing supply and driving down the market price.

  2. 2

    What happens when perfectly competitive firms make losses in the short run?

    Model answer

    Firms exit the market, reducing supply and driving up the market price.

  3. 3

    What level of profit do perfectly competitive firms earn in long-run equilibrium?

    Model answer

    Only normal profit, where total revenue equals total cost.

  4. 4

    Why can perfectly competitive firms only earn normal profit in the long run?

    Model answer

    Because supernormal profits attract entry which drives price down, and losses cause exit which drives price up, until only normal profit remains.

  5. 5

    State the condition relating price and average total cost in long-run equilibrium for perfect competition.

    Model answer

    Price equals minimum average total cost (P = min ATC).

  6. 6

    State the full equilibrium condition showing the relationship between MC, MR, AR and ATC in long-run equilibrium for a perfectly competitive firm.

    Model answer

    MC = MR = AR = ATC at the equilibrium output.

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