Firms in Perfectly Competitive Markets

12.1 Perfectly Competitive Markets

A perfectly competitive market is a foundational concept in microeconomics, characterized by specific conditions that lead to unique firm behavior and market outcomes.

• Definition: A market structure where there are many buyers and sellers, all firms sell identical products, and there are no barriers to entry or exit.

• Price Takers: Firms and buyers are too small to affect the market price; they must accept the prevailing market price.

• Horizontal Demand Curve: Each firm faces a perfectly elastic (horizontal) demand curve at the market price.

• Examples: Agricultural markets (e.g., wheat, poultry farming) are often close to perfectly competitive.

Table: The Four Market Structures

12.2 How a Firm Maximizes Profit in a Perfectly Competitive Market

Firms in perfectly competitive markets aim to maximize profit by choosing the optimal level of output.

• Profit Formula:

• Revenue Relationships: In perfect competition,

• Average Revenue (AR):

• Marginal Revenue (MR):

• Profit Maximization Rule: Produce the quantity where (marginal cost).

• Additional Rule for Perfect Competition: Since , profit is maximized where .

Example Table: Farmer Parker's Revenue and Profit

Additional info: The profit-maximizing output is where MR = MC, which is at 7 bushels in this example.

12.3 Illustrating Profit or Loss on the Cost Curve Graph

Graphs are used to visually represent a firm's profit or loss at different output levels.

• Profit Calculation:

• Interpretation: The area between price and average total cost (ATC) at the profit-maximizing quantity represents total profit (or loss if ATC > P).

• Common Error: Maximizing profit per unit (minimum ATC) is not the same as maximizing total profit.

Example: If price is above ATC at the profit-maximizing output, the firm earns a profit; if below, it incurs a loss.

12.4 Deciding Whether to Produce or to Shut Down in the Short Run

Firms may face losses in the short run and must decide whether to continue production or temporarily shut down.

• Fixed Costs: These are sunk costs and should not affect the shutdown decision.

• Shutdown Rule: Shut down if total revenue is less than variable cost, or equivalently, if (average variable cost).

• Supply Curve: The firm's marginal cost curve above AVC is its short-run supply curve.

Equation:

12.5 Entry and Exit of Firms in the Long Run

In the long run, the entry and exit of firms ensure that perfectly competitive firms earn zero economic profit.

• Economic Profit: Attracts new firms, increasing supply and lowering price until profit is eliminated.

• Economic Loss: Causes firms to exit, reducing supply and raising price until losses are eliminated.

• Long-Run Equilibrium: Occurs when firms break even (P = minimum ATC), and no new firms enter or exit.

• Long-Run Supply Curve: Horizontal at the minimum point of the typical firm's average cost curve in a constant-cost industry.

Industry Variations:

• Increasing-Cost Industry: Entry raises input prices, causing an upward-sloping long-run supply curve.

• Decreasing-Cost Industry: Entry lowers costs (e.g., economies of scale), causing a downward-sloping long-run supply curve.

12.6 Perfect Competition and Efficiency

Perfect competition leads to both productive and allocative efficiency in the long run.

• Productive Efficiency: Goods are produced at the lowest possible cost (P = minimum ATC).

• Allocative Efficiency: Production matches consumer preferences; every good is produced up to the point where marginal benefit equals marginal cost (P = MC).

• Benchmark: These efficiencies serve as standards to evaluate real-world market performance.

Example: In the egg market, entry and exit of farmers in response to profit opportunities drive prices to the break-even level, ensuring efficiency.