Perfect Competition

Work in progress. This note is still being written and incomplete.

Perfect competition is a theoretical market structure with a large number of buyers and sellers selling identical products.

Perfect competition does not commonly exist in its pure form.

Agricultural markets are often considered close examples.

Conditions for Perfect Competition

  1. Many buyers and sellers
    No individual buyer or seller can control the market.

  2. Identical products
    Products from different sellers are the same.

  3. Informed buyers and sellers
    Buyers and sellers have information about prices and product quality.

  4. Free entry and exit
    Firms can enter when profits are available and leave when they experience losses.

Price Taker

A perfectly competitive firm is a price taker.

The market determines the equilibrium price, and an individual firm must accept that price.

Therefore, the demand curve facing an individual firm is horizontal.

Entry and Exit of Firms

Economic Profit

Economic profit attracts new firms into the market.

Economic Profit→New Firms Enter→Market Supply Increases→Price Falls\text{Economic Profit} \rightarrow \text{New Firms Enter} \rightarrow \text{Market Supply Increases} \rightarrow \text{Price Falls}

Entry continues until economic profit becomes zero.

Economic Loss

Economic loss causes some firms to leave the market.

Economic Loss→Firms Exit→Market Supply Decreases→Price Rises\text{Economic Loss} \rightarrow \text{Firms Exit} \rightarrow \text{Market Supply Decreases} \rightarrow \text{Price Rises}

Exit continues until firms return to normal profit.

Efficiency

Perfect competition can achieve:

Productive Efficiency

Firms produce goods at the lowest possible cost.

Allocative Efficiency

Resources are allocated toward the goods consumers want.

MR=MCMR = MC

Dynamic Efficiency

Firms have incentives to innovate and adapt to changes in consumer preferences.

Written by September 26, 2026 2 min read
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