Perfect Competition (Price and Output Determination)

1) Meaning: what is perfect competition?

Perfect competition is a market structure characterized by many buyers and sellers such that no single buyer or seller can influence the market price. The firm is a price taker.

A perfectly competitive industry determines the market price through demand and supply. Each individual firm takes that price as given and chooses output to maximize profit.

2) Assumptions / features (very testable)

Standard conditions:

1. Large number of firms and buyers → individual firm is small relative to market.
2. Homogeneous product → perfect substitutes across firms (e.g., wheat of same grade).
3. Free entry and exit in the long run → no barriers.
4. Perfect information for buyers and sellers.
5. Perfect mobility of factors (often assumed).
6. No selling costs / advertising (in the pure model).
7. Firms are profit maximizers.

CUET caution: If product is differentiated or entry is restricted, perfect competition assumptions break.

3) Demand curve for a competitive firm: why perfectly elastic?

Because the firm is a price taker:

• If it charges above market price, it sells nothing.
• If it charges below, it can sell any amount but would earn less per unit (unnecessary).

Hence, the firm faces a horizontal demand curve at market price $P$.

So:

• Average Revenue (AR) = Price (P)
• Marginal Revenue (MR) = Price (P) Thus:

This is one of the most asked MCQ facts.

4) Firm’s objective and profit

Profit:

In perfect competition:

So:

5) Short-run equilibrium of a competitive firm

5.1 Profit maximization rule

A firm maximizes profit where:

But since $MR = P$ under perfect competition:

Second-order condition: MC must be rising at equilibrium (intersect from below).

5.2 Output decision (short run)

Depending on price relative to costs, firm may:

• earn supernormal profit,
• earn normal profit,
• incur loss but continue,
• shut down.

6) Shutdown condition in the short run (high-yield)

Even if the firm makes a loss, it may produce if it can cover variable costs.

6.1 Shutdown point

A competitive firm shuts down in the short run if:

Because if price is below minimum average variable cost, revenue cannot even cover variable costs.