뒤로The Competitive Firm and Market Supply Curves: Microeconomics Study Notes
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The Competitive Firm
Definition and Characteristics
A competitive firm operates in a market where it takes the price as given, ignores the actions of rival firms, and does not engage in strategic behavior. The market determines the price, and individual firms, such as wheat farmers or small businesses, are typical examples.
Price Taker: The firm cannot influence the market price.
Demand Curve: The demand curve faced by a competitive firm is perfectly elastic at the market price.
Revenue Relationships:
Total Revenue (TR):
Marginal Revenue (MR):
Average Revenue (AR):
For a price-taking firm:
Output Determination of a Competitive Firm
Profit Maximization
Firms aim to maximize profit, defined as the difference between total revenue and total cost:
Profit:
Profit Maximizing Condition: Profits are maximized when . For a competitive firm, , so the condition becomes .
Profit vs. Rent
Profit:
Rent: (avoidable opportunity cost)
Producer's Surplus: Rent is also known as Producer's Surplus, representing gains from trade on the production side.
Graphical Representation of TVC, Rent, and Profit
Method 1: The area under the MC curve represents TVC.
Method 2: The rectangle area .
Individual Supply Curve
The difference between profit and rent is crucial for deriving the individual firm's supply curve.
As long as , the firm is willing to produce in the short run (). This is the shutdown point (minimum AVC).
When , the firm does not make a loss (). This is the breakeven point (minimum AC).
The firm's supply curve is the MC curve above the shutdown point.
The individual supply curve is always upward-sloping.
Equilibrium Profit
Understanding Economic Profit
Economic Profit:
Total Cost:
Example: Jake's Yumburger stall illustrates explicit costs, accounting profit, economic costs, and economic profit.
Economic Profit in Equilibrium
In equilibrium, competitive firms earn zero economic profit.
Entry or exit of firms adjusts output price, eliminating profit or loss.
If profit is due to a special factor input, its opportunity cost rises until profit is eliminated.
In equilibrium: (the "trinity" of competitive equilibrium).
Firms can earn rent (payment to the fixed factor of production) even with zero profit.
Market Supply Curve
Definition and Construction
The market supply curve is the sum of individual supply curves, considering the market structure and distribution of firms.
Identical Firms: If all firms are identical (no sunk costs, same AC and MC), the market supply curve is flat: , .
Different Firms: Firms may differ in fixed/sunk costs, affecting AVC and AC. Firms with lower AVC produce first as price rises, and others enter as price increases.
The market supply curve is upward-sloping, reflecting both intensive and extensive margin adjustments.
Equilibrium Outcomes
The marginal firm earns zero profit and zero rent.
Intra-marginal firms earn zero profit but positive rent.
Summary Table: Key Concepts
Concept | Formula | Condition |
|---|---|---|
Total Revenue (TR) | -- | |
Marginal Revenue (MR) | for profit maximization | |
Average Revenue (AR) | for competitive firm | |
Profit | for breakeven | |
Rent (Producer's Surplus) | for shutdown point |
Additional info: Academic context was added to clarify the graphical methods for identifying TVC, rent, and profit, and to explain the distinction between economic profit and rent in equilibrium.
