Perfect Competition and Firm Behavior in Microeconomics

Learning Objectives

• Explain a perfectly competitive firm's profit-maximizing choices and derive its supply curve.

• Explain how output, price, and profit are determined in the short run.

• Explain how output, price, and profit are determined in the long run and explain why perfect competition is efficient.

Market Types

Overview of Market Structures

Microeconomics classifies markets based on the number of firms, product differentiation, and barriers to entry. The four main market types are:

• Perfect Competition

• Monopoly

• Monopolistic Competition

• Oligopoly

Perfect Competition

Perfect competition exists when:

• Many firms sell an identical product to many buyers.

• There are no barriers to entry or exit from the market.

• Established firms have no advantage over new firms.

• Sellers and buyers are well informed about prices.

Examples include wheat farming, fishing, wood pulping, and paper milling. In perfect competition, firms are price takers and face a perfectly elastic demand curve.

Other Market Types

• Monopoly: One firm sells a good or service with no close substitutes and significant barriers to entry. Examples: local utilities, patented drugs.

• Monopolistic Competition: Many firms sell similar but slightly differentiated products. Examples: restaurants, clothing brands.

• Oligopoly: A few interdependent firms dominate the market. Examples: airplane manufacturing, soft drinks (Coke and Pepsi).

15.1 A Firm's Profit-Maximizing Choices

Profit Maximization

A firm's objective is to maximize economic profit, which is the difference between total revenue and total cost. In the short run, the firm chooses the quantity of output that maximizes profit.

• Normal profit: The return that the firm's entrepreneur can obtain on average, just for being in business.

• Economic profit: Total revenue minus total cost, including opportunity costs.

Price Taker

In perfect competition, firms are price takers. They sell at the market price and cannot influence it. The demand curve facing an individual firm is perfectly elastic.

• Firms choose output at the going price, but none above that price.

• Each firm's product is a perfect substitute for others in the market.

Revenue Concepts

• Total Revenue (TR): The price multiplied by the quantity sold. $TR = P imes Q$

• Marginal Revenue (MR): The change in total revenue from selling one more unit. In perfect competition, $MR = P$.

In perfect competition, marginal revenue equals price, and the total revenue curve is a straight line from the origin with slope equal to the market price.

Profit-Maximizing Output

Profit is maximized at the output level where the vertical distance between the total revenue and total cost curves is greatest. This is where economic profit is highest.

• As output increases, total revenue increases linearly, but total cost increases nonlinearly due to diminishing returns.

• There is one output level that maximizes economic profit.

Example Table: Revenue, Cost, and Profit

Quantity (Q) cans/day	Total Revenue (TR) dollars/day	Total Cost (TC) dollars/day	Economic Profit (TR-TC) dollars/day
0	0	14	-14
4	32	46	-14
8	64	62	2
10	80	51	29
13	104	75	29

Additional info: The table shows that profit is maximized at 10 and 13 cans per day, with a maximum economic profit of $29 per day.

Marginal Analysis and the Supply Decision

Marginal analysis compares marginal revenue (MR) and marginal cost (MC) to find the profit-maximizing output.

• If $MR > MC$, increasing output increases profit.

• If $MR < MC$, decreasing output increases profit.

• If $MR = MC$, profit is maximized.

Formula:

$MR = MC$

At the profit-maximizing output, marginal revenue equals marginal cost.

Example Table: Marginal Analysis

Quantity (Q) cans/day	Total Revenue (TR) dollars/day	Total Cost (TC) dollars/day	Marginal Cost (MC) dollars	Marginal Revenue (MR) dollars	Economic Profit (TR-TC) dollars/day
9	72	50	12	8	22
10	80	51	8	8	29
11	88	54	13	8	34

Additional info: Profit is maximized when $MR = MC$ at 10 cans per day.

Key Terms

• Perfect competition: Market with many firms selling identical products, no barriers to entry, and price-taking behavior.

• Price taker: A firm that cannot influence the market price and must accept it as given.

• Marginal revenue: The change in total revenue from selling one more unit.

• Marginal cost: The change in total cost from producing one more unit.

• Economic profit: Total revenue minus total cost, including opportunity costs.

Summary

• Perfect competition leads to efficient allocation of resources and maximizes consumer and producer surplus.

• Firms maximize profit by producing where $MR = MC$.

• In the short run, firms may earn economic profit, break even, or incur losses.

• In the long run, entry and exit drive economic profit to zero, and only normal profit remains.