Perfect Competition in the Short Run

Four Basic Market Structures

The structure of a market determines the behavior of firms and the outcomes for consumers. The four main market structures are:

• Perfect Competition: Many firms, identical products, no barriers to entry, price takers.

• Monopolistic Competition: Many firms, differentiated products, some barriers to entry, some price-setting power.

• Oligopoly: Few firms, products may be identical or differentiated, significant barriers to entry, interdependent pricing.

• Monopoly: One firm, unique product, high barriers to entry, price maker.

Market Structure Continuum: Perfect competition (many firms) → Monopoly (one firm).

Characteristics of Perfect Competition

• Very large number of sellers (e.g., 1000).

• Standardized (homogeneous) product.

• Firms are price takers—they accept the market equilibrium price.

• Free entry and exit from the market.

• Firm’s demand curve is perfectly elastic (horizontal).

All firms sell at the same market price, determined by the intersection of market demand and supply.

Revenue Concepts in Perfect Competition

• Total Revenue (TR):

• Average Revenue (AR):

• Marginal Revenue (MR):

In perfect competition, for all units sold.

Profit Maximization in the Short Run

Firms in perfect competition maximize profit (or minimize loss) by choosing the output level where:

• Marginal Revenue equals Marginal Cost:

• Alternatively, where the difference is the greatest.

Key decisions:

1. What quantity to produce?

2. Whether to produce at all (shut down or operate)?

Short-Run Supply Curve

The firm’s short-run supply curve is the portion of its marginal cost (MC) curve that lies above the minimum average variable cost (AVC).

• If , the firm produces where .

• If , the firm shuts down in the short run.

Market Entry and Exit

• Entry of new firms increases supply, lowers price, and eliminates economic profits.

• Exit of firms decreases supply, raises price, and eliminates losses.

Long-Run Equilibrium in Perfect Competition

In the long run, firms can freely enter or exit the market. The result is:

• Firms earn zero economic profit (normal profit).

• Price equals minimum average total cost: .

• Productive and allocative efficiency are achieved: .

Industry Cost Structures

• Constant-Cost Industry: Entry/exit does not affect resource prices or costs.

• Increasing-Cost Industry: Entry raises resource prices and costs.

• Decreasing-Cost Industry: Entry lowers resource prices and costs.

Efficiency and Creative Destruction

• Productive Efficiency: Producing at lowest possible cost ().

• Allocative Efficiency: Resources are allocated where they are most valued ().

• Creative Destruction: Innovation leads to new products/methods, making old ones obsolete.

Monopoly

Characteristics of Monopoly

• Single seller (the industry).

• No close substitutes for the product.

• Price maker—controls the market price.

• High barriers to entry (e.g., economies of scale, legal barriers, resource ownership).

• Non-price competition (advertising, PR).

Barriers to Entry

• Economies of scale (cost advantages for large-scale production).

• Legal barriers (patents, licenses).

• Ownership of essential resources.

• Strategic pricing to deter entry.

Monopoly Demand and Revenue

• The monopolist faces the market demand curve, which is downward sloping.

• Marginal revenue (MR) is always less than price (P) for a monopolist.

• To sell more, the monopolist must lower the price on all units sold.

Profit Maximization for a Monopolist

The monopolist maximizes profit by producing the quantity where and charging the highest price consumers are willing to pay for that quantity (from the demand curve).

1. Find output where .

2. Find price from the demand curve at that output.

3. Calculate profit as .

Economic Effects of Monopoly

• Monopoly price () is higher and output () is lower than in perfect competition (, ).

• Monopoly is less efficient: and .

• Results in deadweight loss and income transfer from consumers to the monopolist.

Regulation of Monopoly

• Governments may regulate natural monopolies (e.g., utilities) to prevent excessive pricing.

• Regulatory options:

  • Socially optimal price: (may result in losses for the firm).

  • Fair-return price: (firm earns normal profit).

Summary Table: Comparison of Perfect Competition and Monopoly

Key Equations

• Total Revenue:

• Average Revenue:

• Marginal Revenue:

• Profit Maximization: