Edexcel A-Level Economics A 9EC0
The Nature of Economics
How Markets Work
Market Failure
Government Intervention
Measures of Economic Performance
Aggregate Demand
Aggregate Supply
National Income
Economic Growth
Macroeconomic Objectives and Policies
Business Growth
Business Objectives
Revenues, Costs and Profits
Market Structures
The Labour Market
Government Intervention in Markets
International Economics
Poverty and Inequality
Emerging and Developing Economies
The Financial Sector
The Role of the State in the Macroeconomy
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.
On a diagram showing short-run supernormal profit, how is the profit area represented?
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
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
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
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
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
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
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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