Perfect competition is a market structure where many sellers offer the same product, so no single seller can control the price. It matters because it shows how supply and demand can set prices when competition is very strong. A farmers market with many stalls selling identical baskets of wheat is a useful model.
Each seller must accept the market price because buyers can easily switch to another seller.
Key Facts
- In perfect competition, there are many buyers and many sellers.
- Products are identical, so buyers see no difference between one seller's product and another's.
- Each firm is a price taker, meaning it accepts the market price instead of setting its own.
- For a competitive firm, marginal revenue equals price: MR = P.
- Profit is total revenue minus total cost: Profit = TR - TC.
- A profit-maximizing firm produces where marginal revenue equals marginal cost: MR = MC.
Vocabulary
- Perfect competition
- A market structure with many buyers and sellers, identical products, easy entry and exit, and firms that take the market price.
- Price taker
- A seller that must accept the market price because it is too small to influence the overall market.
- Identical product
- A good that buyers view as the same no matter which seller provides it.
- Marginal revenue
- The extra revenue a firm earns from selling one more unit of output.
- Market price
- The price determined by the interaction of total market supply and total market demand.
Common Mistakes to Avoid
- Thinking a competitive seller can raise its price above the market price and keep most customers. This is wrong because buyers can switch to many other sellers offering the same product at the lower market price.
- Confusing many sellers with perfect competition by itself. Many sellers are important, but perfect competition also requires identical products, easy entry and exit, and good market information.
- Assuming firms always earn large profits in perfect competition. This is wrong because easy entry can attract new firms, increase supply, and push economic profit toward zero in the long run.
- Using total revenue instead of marginal revenue to choose output. A competitive firm should compare the extra revenue from one more unit with the extra cost, so the key rule is MR = MC.
Practice Questions
- 1 A wheat seller in a perfectly competitive market sells 80 baskets at a market price of $6 each. What is the seller's total revenue?
- 2 A firm has marginal cost values of 5, 9 for producing its 1st through 4th units. If the market price is $7, how many units should it produce to follow the MR = MC rule as closely as possible?
- 3 In a market with many sellers offering identical bottled water, one seller raises its price from 1.25 while others stay at $1.00. Explain what is likely to happen to that seller's sales and why.