The characteristics of perfect competition

Perfect competition describes a market structure where numerous firms operate under ideal conditions that prevent any single firm from influencing prices.

Key features of a perfectly competitive market

• Large number of firms - The market consists of many small firms, none of which can control prices due to their insignificant market share.
• Homogeneous products - All firms produce identical goods or services, making them perfect substitutes.
• No barriers to entry or exit - Firms can freely enter or leave the market without facing restrictions.
• Perfect information - Both buyers and sellers have complete knowledge about prices, product quality, and availability.
• Perfect factor mobility - Resources like labour and capital can move freely between firms and industries without obstacles.

Demand and revenue curves in perfect competition

In perfect competition, individual firms cannot set their own prices because of the market's structure. Instead, they respond to the overall market price established by supply and demand.

The nature of demand for a perfectly competitive firm

Firms in this market are price-takers, meaning they must accept the price determined by the interaction of total market supply and demand. This occurs because there are many sellers offering identical products, and buyers have full information to switch easily between them.

Revenue curves

• The demand curve facing an individual firm is horizontal and perfectly elastic at the market price, reflecting that the firm can sell any quantity at that price.
• This demand curve also represents the average revenue (AR) curve, as AR is the price per unit sold.
• The marginal revenue (MR) curve coincides with the AR curve, since selling an extra unit brings in revenue equal to the fixed market price.

Profit maximisation and equilibrium in the short run

Perfectly competitive firms aim to maximise profits by choosing the output level where the additional revenue from selling one more unit equals the additional cost of producing it.

Rule for profit maximisation

Firms produce at the quantity where marginal revenue (MR) equals marginal cost (MC).

Determining profit levels

Profit status depends on the comparison between average revenue (AR) and average total cost (ATC) at the profit-maximising output:

• If AR > ATC, the firm earns supernormal (positive economic) profits.
• If AR = ATC, the firm earns normal profits, covering all costs including opportunity costs.
• If AR < ATC, the firm makes losses.

In the short run, if the market price is above average total cost, firms earn supernormal profits.

Equilibrium in the long run

Over time, the absence of entry barriers allows the market to adjust through firm entry and exit, eliminating supernormal profits or losses and restoring equilibrium.

Process of long-run adjustment

• When supernormal profits exist - New firms enter the market, increasing overall supply, which lowers the market price until supernormal profits disappear and only normal profits remain.
• When losses occur - Firms exit the market, reducing overall supply, which raises the market price until losses are eliminated and normal profits are achieved.

Conditions for long-run equilibrium

In the long run, equilibrium occurs where price (P) equals average revenue (AR), marginal revenue (MR), marginal cost (MC), and average total cost (ATC). At this point, firms maximise profits (MR = MC) while earning only normal profits (AR = ATC), with no incentive for further entry or exit.

Efficiency and benefits of perfect competition

Perfect competition promotes efficient resource use and maximises societal benefits.

Types of efficiency achieved

• Allocative efficiency - Resources are distributed optimally from society's viewpoint, as the price equals marginal cost (P = MC) for the last unit produced.
• Productive (technical) efficiency - In the long run, firms produce at the minimum average total cost, ensuring no waste of scarce resources.

Broader benefits of perfect competition

• Lowest possible prices for consumers - Competition drives prices down to the level of marginal cost, benefiting buyers.
• No market power for firms - Individual sellers cannot influence prices, preventing exploitation.
• Optimal resource allocation - Market forces ensure goods are produced in quantities that maximise social welfare, defined as the total of consumer and producer surplus.
• Benchmark for policy - Policymakers use this model to assess real markets; if prices greatly exceed marginal costs, interventions like regulations may be considered to improve efficiency.