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.
Price Elasticity of Demand: For a price-taking firm, the price elasticity of demand is infinite.
Revenue Concepts
Total Revenue (TR):
Marginal Revenue (MR):
Average Revenue (AR):
For a competitive 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 determines the optimal output .
Profit vs. Rent
Profit:
Rent: (avoidable opportunity cost)
Producer's Surplus: Rent is also called Producer's Surplus, measuring 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, which occurs when (shutdown point: minimum AVC).
When , the firm does not make a loss, which occurs when (breakeven point: minimum AC).
The firm supply curve is the MC curve above the shutdown point (minimum AVC), and 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 still earn rent (producer's surplus) in equilibrium, which equals payment to the fixed factor of production.
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 at , and .
Different Firms: If firms differ in fixed/sunk costs, those with lower AVC produce first as price rises, followed by others (intensive and extensive margin adjustments).
The market supply curve is upward-sloping, reflecting the sum of individual firm supply curves.
Equilibrium Outcomes
The marginal firm earns zero profit and zero rent in equilibrium.
Intra-marginal firms earn zero profit but positive rent.
Summary Table: Key Concepts
Concept | Formula | Condition |
|---|---|---|
Total Revenue (TR) | -- | |
Marginal Revenue (MR) | -- | |
Average Revenue (AR) | -- | |
Profit Maximization | Competitive firm: | |
Shutdown Point | Rent | |
Breakeven Point | Profit | |
Economic Profit | Zero in equilibrium | |
Producer's Surplus (Rent) | Positive in equilibrium |
Additional info: Academic context was added to clarify the graphical methods for finding TVC, rent, and profit, and to explain the intensive and extensive margin adjustments in market supply.
