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EconomicsModule 1 of 8

The Firm and Market Structures

7

Concepts

6

Formulas

1

Decisions

5

Quiz Questions

Key Concepts

7 concepts covered in this module.

Perfect Competition

Many firms, identical products, no barriers to entry. Price takers. P = MR = MC in long run. Zero economic profit in LR.

Monopolistic Competition

Many firms, differentiated products, low barriers. Downward-sloping demand. Zero economic profit in LR due to entry.

Oligopoly

Few large firms, high barriers, interdependent pricing. Game theory applies. Nash equilibrium: each firm optimizes given others' choices.

Monopoly

Single seller, unique product, very high barriers. Price maker. MR < P. Can earn economic profit in long run.

Profit Maximization

All firms maximize profit where MR = MC. If P > ATC: economic profit. If AVC < P < ATC: operate at a loss. If P < AVC: shut down.

Economies of Scale

LRAC decreases as output increases. Minimum efficient scale: output where LRAC is first minimized.

Concentration Measures

N-firm ratio and HHI measure market concentration. HHI = sum of squared market shares. HHI > 2,500 = highly concentrated.

Formulas

6 essential formulas for this module.

Profit Maximization

MR = MC

Where: MR = marginal revenue, MC = marginal cost

Total Revenue

TR = P × Q

Where: P = price, Q = quantity

Economic Profit

π = TR - TC (including opportunity costs)

Where: TC = explicit + implicit costs

HHI

HHI = Σ(market sharei

Where: Sum of squared % market shares

Breakeven

TR = TC or P = ATC

Where: Zero economic profit point

Shutdown (Short Run)

P < AVC → shut down

Where: Cannot cover variable costs

Decision Frameworks

1 decision frameworks to guide your analysis.

Operate or Shut Down in Short Run?

  • Operate: P ≥ AVC (covers variable costs, contributes to fixed costs)
  • Shut down: P < AVC (better to produce nothing)

Mind Map

Visual overview of how concepts connect in this module.

Market Structures
Perfect Competition
Many firms, identical products
Price taker: P = MR
Zero LR economic profit
No barriers to entry
Monopolistic Competition
Differentiated products
Downward-sloping demand
Zero LR economic profit
Low barriers
Oligopoly
Few firms, interdependent
Game theory / Nash equilibrium
Kinked demand curve
High barriers
Monopoly
Single seller
Price maker: MR < P
Can earn LR economic profit
Very high barriers
Key Relationships
MR = MC for all
P > AVC to operate
Economies of scale
HHI concentration

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