How are price and output determined under perfect competition? [5]

Under perfect competition, price and output are determined by the interaction of market supply and demand at the industry level, where individual firms are price takers. The determination process involves the following key steps:

1. Market Demand and Supply

• The market demand curve slopes downward, reflecting the law of demand: as price falls, quantity demanded rises.
• The market supply curve slopes upward, reflecting the law of supply: as price rises, quantity supplied increases.
• The equilibrium price (P)* and equilibrium quantity (Q)* are determined where market demand equals market supply (i.e., where D = S).

2. Individual Firm’s Decision

• Each firm in perfect competition is a price taker, meaning it accepts the market-determined price (P)* as given.
• The firm maximizes profit where Marginal Revenue (MR) = Marginal Cost (MC).
• Since Price (P) = Average Revenue (AR) = MR in perfect competition, the profit-maximizing output occurs where P = MC.
• The firm produces at the point where MC curve intersects the horizontal price line (P)*.

3. Short-Run Equilibrium

• If P > AVC (Average Variable Cost), the firm operates (even at a loss if P < ATC).
• If P < AVC, the firm shuts down in the short run.
• The short-run industry supply curve is the sum of individual firms’ MC curves above AVC.

4. Long-Run Equilibrium

• In the long run, firms earn normal profit (P = ATC) because:
  • If P > ATC, firms enter, increasing supply and driving price down.
  • If P < ATC, firms exit, reducing supply and driving price up.
• The long-run equilibrium occurs where:
  • P = MC = ATC (minimum point).
  • Market demand equals long-run supply.

Graphical Representation

• P* is the equilibrium price set by market demand and supply.
• Each firm produces Q* where P = MC*.
• In the long run, P = MC = ATC (minimum)*.

Key Conditions for Perfect Competition

• Large number of buyers and sellers (no single firm influences price).
• Homogeneous product (no differentiation).
• Free entry and exit (no barriers).
• Perfect information (all firms know market price and costs).

This ensures that price and output are determined efficiently, maximizing social welfare.