Short-Run Firms

Basic Assumptions about Firms

In microeconomics, the analysis of firm behavior begins with two fundamental assumptions:

• Profit Maximization: Firms aim to maximize their profits.

• Rational Decision-Making: Firms make decisions logically, based on available information.

Price Takers

A price taker is a firm that cannot influence the market price and must accept the prevailing price for its product.

• Occurs when there are many small firms in a market, each with a negligible share.

• Firms are price takers because their individual output is too small to affect market price.

• Example: Wheat farmers in a competitive market.

Production Function

The production function describes the relationship between inputs (such as labor and capital) and output.

• Captures the technology used by firms to transform inputs into outputs.

• Example: , where is output, is capital, and is labor.

Accounting Profits

Accounting profit is the difference between total revenue and explicit costs.

• Formula:

• Example: If , , , , , , then:

Economic Profits

Economic profit considers both explicit and implicit (opportunity) costs.

• Formula:

• Economic profit is always less than or equal to accounting profit.

Time Frames in Firm Behavior

Firm behavior is analyzed over three time frames:

• Short Run: At least one input is fixed (usually capital).

• Long Run: All inputs are variable.

• Very-Long Run: Technology itself can change.

Marginal Product of Labour (MPL)

The Marginal Product of Labour (MPL) is the additional output produced by one more unit of labor.

• Formula:

• MPL is assumed to be positive, but may diminish as more labor is added (law of diminishing returns).

• Example: If and , then

Cost Concepts

• Fixed Costs (FC): Costs that do not vary with output (e.g., rent).

• Variable Costs (VC): Costs that change with output (e.g., wages).

• Total Costs (TC):

Average and Marginal Costs

• Average Fixed Cost (AFC):

• Average Variable Cost (AVC):

• Average Total Cost (ATC):

• Marginal Cost (MC):

Cost Curve Shapes

• FC: Horizontal line (does not change with Q).

• AFC: Downward sloping (spreads fixed cost over more units).

• VC: Upward sloping (increases with Q).

• AVC: U-shaped (due to diminishing returns).

• TC: Upward sloping, starts at FC.

• ATC: U-shaped (combines AFC and AVC).

• MC: U-shaped (intersects AVC and ATC at their minimums).

Marginal Revenue (MR)

• Marginal Revenue:

• For a price-taking firm,

Profit Maximization

Profit maximization occurs where .

• If , increase output.

• If , decrease output.

• At , profit is maximized.

Shutdown Condition

• A firm will shut down in the short run if economic profits are negative and cannot cover variable costs.

• Shutdown occurs when or .

Short-Run Supply Curve

• The firm's short-run supply curve is its curve above .

Comparative Statics: Examples

• Example 1: If wage rate increases, and increase, so decreases and profits fall.

• Example 2: If productivity increases, increases, decreases, so increases and profits rise.

• Example 3: If price of final product increases, increases, so increases and profits rise.

Summary Table: Cost Concepts

Visual Representation

• Profit maximization occurs where and curves intersect.

• Accounting profits are the vertical distance between and curves at the profit-maximizing output.

Additional info: These notes expand on the original questions by providing definitions, formulas, and examples for each concept, ensuring a self-contained study guide for short-run firm analysis in microeconomics.