Wize University Microeconomics Textbook > Monopolistic Competition
Short Run vs Long Run Equilibrium
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Short and Long Run Equilibrium
In the short run a firm in monopolistic competition can make a profit or a loss, but in the long run they will make zero profit.
Short Run with Economic Profit

- In the short run the business will maximize its profit where Marginal Revenue (MR) = Marginal Cost (MC). In the diagram above, this would occur at an output of40.
- Plug this quantity in the demand to get the price which would be$70
- Plug this quantity in the ATC which would be$60
- Calculate the profit using the formula Profit = (P - ATC) * Q =(70 - 60) * 40 = $400
- Since the business is making a profit, other firms willenterthe industry in the long run and this will cause the demand for the existing firms to shift to theleft.
Long Run

- In the long run the demand will keep shifting left until it is just touching (tangent to) the ATC curve and MR = MC still.
- The output in the long run would be30units
- Plug this quantity in demand to get the price which would be$50
- Plug this quantity in ATC which would be$50
- Profit =(50 - 50) * 30 = 0. In the long run every firm is making 0 profit in monopolistic competition.
Short Run with Economic Loss

- In the short run we still make MR = MC. In the diagram above, this would occur at an output of20.
- Plug this quantity in the demand to get the price which would be$40
- Plug this quantity in the ATC which would be$45
- Calculate the profit using the formula Profit = (P - ATC) * Q =(40 - 45) * 20 = $-100
- Since the business is making a loss, other firms willexitthe industry in the long run and this will cause the demand for the existing firms to shift to theright.

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Example: Short and Long Run Equilibrium
A firm in a monopolistic competition produces the level of output at which
A) the marginal revenue equals marginal cost
B) the marginal social cost equals marginal social benefit
C) the demand curve equals the supply curve
D) the marginal revenue equals price
A
MR = MC is true for all market structures. When we plug that output in to the demand the price would higher than the marginal revenue.
Practice: Long Run Equilibrium
What is true of a monopolistically competitive market in long-run equilibrium?