Microeconomics Foundations (ECON 101) · Module 6 of 9
Perfect Competition
How price-taking firms decide how much to produce, and why profits vanish in the long run.
Characteristics of Perfect Competition
- Perfect competition features many small firms, identical (homogeneous) products, easy entry and exit, and perfect information, making every firm a "price taker.".
Why is a firm in a perfectly competitive market called a "price taker"?
Solution. Because with many firms selling identical products, no single firm has enough market share to influence the market price — each firm must accept ("take") the price set by the overall market.
Profit Maximization: MR = MC
- A firm maximizes profit by producing the quantity where marginal revenue (MR) equals marginal cost (MC); producing beyond this point costs more than it earns, and producing less forgoes profitable output.
- In perfect competition, marginal revenue equals the market price, since a firm can sell additional units without lowering the price.
Why does a firm maximize profit specifically where MR = MC, rather than at some other quantity?
Solution. If MR > MC, producing one more unit adds more revenue than cost, increasing profit, so the firm should keep producing; if MR < MC, that unit costs more than it earns, so the firm should produce less; profit is maximized exactly where the two are equal.
Shutdown & Break-Even Points
- In the short run, a firm should shut down (temporarily stop producing) if the market price falls below its minimum average variable cost, since it isn't even covering variable costs.
- The break-even point occurs where price equals minimum average total cost — the firm earns zero economic profit (normal profit) at that price.
Why might a firm continue operating in the short run even while losing money, as long as price stays above average variable cost?
Solution. As long as price covers average variable cost, the firm is earning enough to cover its variable costs and at least partially cover its fixed costs, which it would still have to pay even if it shut down; producing is thus better than shutting down entirely in that situation.
Long-Run Equilibrium in Perfect Competition
- In the long run, if firms are earning positive economic profit, new firms enter the industry, increasing supply and driving price down until economic profit is zero; the reverse happens if firms are suffering losses.
- Long-run equilibrium in perfect competition occurs where price equals minimum long-run average total cost, and firms earn zero economic profit (normal profit).
Why can't firms in a perfectly competitive market earn positive economic profit in the long run?
Solution. Positive economic profit attracts new firms to enter the industry, since entry is easy in perfect competition, increasing total market supply and driving the price down until economic profit falls to zero.
Check yourself
2 of this module's 5 quiz questions. Pick your answers, then check them in the app, with an explanation for every question.
1. Why is a firm in perfect competition called a "price taker"?
2. What rule maximizes a firm's profit?