Perfect Competition: Short-Run and Long-Run Market Dynamics, Profit Maximization, and Market Structures

Learning Objectives for Perfect Competition

Understand the key features and characteristics of a perfectly competitive market.
Analyse price and output decisions in the short-run and long-run within a perfectly competitive market.
Explain why the supply curve is equivalent to the marginal cost curve in perfectly competitive markets.
Reference materials include:
- Gillespie, A. (2019). Foundations of Economics (5th ed.). Oxford: Oxford University Press. Chapter 12.
- Sloman, J. & Garratt, D. (2019). Essentials of Economics (8th ed.). England: Pearson. Chapter 6 (Sections 6.1, 6.2).

Definition and Objectives of a Firm

Definition of a Firm:
- A firm is an institution that buys or hires factors of production and organizes them to produce and sell goods and services.
- It serves as an independent unit for producing goods and services for sale.
Objectives of a Firm:
- The primary goal or objective of a firm is to maximize profit and to minimize cost.

Total Approach to Profit Maximization

The Total approach is the simplest method for determining the equilibrium of a firm.
Under Perfect Market:
- The Total Revenue ( $TR$ ) curve is a straight line passing through the origin.
- The firm achieves maximum profits at output level $N$ .
- Profit is maximized where the vertical distance between the $TR$ curve and the Total Cost ( $TC$ ) curve is at its maximum.
Under Imperfect Market:
- The Total Revenue ( $TR$ ) curve continues to rise from left to right but at a less than proportionate rate.
- A rational firm chooses the output $ON$ where the vertical distance between $TR$ and $TC$ is at the maximum.

Profit Maximization: Total Revenue – Total Cost Approach Data

Using a table to determine profit maximization involves scanning for the highest profit value.
Comprehensive Data Table:

Quantity	Total Revenue	Total Cost	Profit/Loss
$0$	$0$	$60$	$-60$
$10$	$100$	$140$	$-40$
$20$	$200$	$210$	$-10$
$30$	$300$	$290$	$10$
$40$	$400$	$390$	$10$
$50$	$500$	$500$	$0$
$60$	$600$	$630$	$-30$
$70$	$700$	$800$	$-100$

Graphical Representation:
- Vertical difference is highest at the quantities ( $30$ to $40$ ) where profit is $10$ .

Marginal Approach to Profit Maximization

A firm is in equilibrium when Marginal Revenue ( $MR$ ) is equal to Marginal Cost ( $MC$ ).
- Rule: $MR = MC$
Under Perfect Market:
- The $MR$ curve is horizontal.
- Equilibrium is achieved where the horizontal $MR$ line intersects the upward-sloping $MC$ curve.
Under Imperfect Market:
- The $MR$ curve is downward sloping.
- Equilibrium is still achieved where $MR = MC$ .

Profit Maximization: Marginal Revenue – Marginal Cost Approach Data

In a perfect market, the $MR$ curve is perfectly elastic or horizontal relative to the price ( $P$ ).

Quantity	Total Revenue	Marginal Revenue	Total Cost	Marginal Cost	Profit/Loss
$0$	$0$	$-$	$60$	$-$	$-60$
$10$	$100$	$10$	$140$	$8$	$-40$
$20$	$200$	$10$	$210$	$7$	$-10$
$30$	$300$	$10$	$290$	$8$	$10$
$40$	$400$	$10$	$390$	$10$	$10$
$50$	$500$	$10$	$500$	$11$	$0$
$60$	$600$	$10$	$630$	$13$	$-30$
$70$	$700$	$10$	$800$	$17$	$-100$

Summary of Observation: At a price of $RM10$ , profit maximization ( $MR=MC$ ) occurs at a quantity of $40$ .

Market Structure Concepts

Definition of a Market:
- An arrangement facilitating the buying and selling of a good, service, factor of production, or future commitment.
- A physical or conceptual place where buyers and sellers meet for transactions.
Definition of a Market Structure:
- Refers to the number and distribution size of buyers and sellers in the market.
- Indicates market shares, degree of product standardization, and ease of entry and exit.

Types of Market Structure

Perfect Competition:
- Large numbers of buyers and sellers.
- Identical (homogenous) products.
- No restrictions on entry and exit.
- Sellers and buyers have perfect knowledge of the market.
Monopoly:
- A single seller and a large number of buyers.
- Products have no close substitutes.
- High entry and exit barriers.
Monopolistic Competition:
- Large numbers of sellers and buyers.
- Differentiated products due to branding and labelling.
- No barriers to entry and exit.
Oligopoly:
- Only a few firms in the industry; large number of buyers.
- Products can be identical or differentiated.
- Barriers to entry and exit exist.

Compartive Market Structure Characteristics

Characteristic	Perfect Competition	Monopolistic Competition	Oligopoly	Monopoly
Number of firms	Very many	Many	Few	One
Type of product	Homogenous	Differentiated	Homogenous or differentiated	Unique: No close substitutes
Entry Conditions	Very easy	Relatively easy	Significant obstacles	Blocked
Control over price	None	Some	Some	Considerable
Price elasticity of demand	Infinite	Large	Small	Very small
Examples	Wheat, corn, cabbages	Food, clothing	Automobiles, petrol, cigarettes	Local phone service, electricity

Perfect Competition: Detailed Characteristics

Definition: A market with many buyers and sellers, homogenous products, and ease of entry/exit.
Core Characteristics:
- Large number of buyers and sellers: Individual firms are "price takers."
- Homogenous or standardized product: Buyers do not distinguish between products from different sellers.
- Free entry and exit: No barriers to firms joining or leaving the industry.
- Perfect knowledge: Everyone knows prices and product quality.
- Perfect mobility of factor of production: Factors can move freely between occupations and locations.
- Absence of transport cost: Costs associated with moving goods are not factored into the model.

Price and Demand in Perfect Competition

Market Level: Price is determined by the intersection of the market supply curve ( $SS$ ) and market demand curve ( $DD$ ).
Firm Level: Since firms are price takers, they face a horizontal demand curve (perfectly elastic).
Equality: For the firm, Price ( $P$ ) = Marginal Revenue ( $MR$ ) = Average Revenue ( $AR$ ).

Equilibrium in Perfect Competition

Equilibrium in the Short Run:
- Firms produce where $MC = MR$ .
- Three possible outcomes:
  1. Abnormal (Supernormal) Profits: Occurs at output $Q^*$ where Average Revenue ( $AR$ ) > Average Cost ( $AC$ ). Point $A$ on the graph.
  2. Losses: Occurs at output $Q^*$ where AR < AC. Point $B$ on the graph.
  3. Normal Profit (Breakeven): Occurs at output $Q^*$ where $AR = AC$ . Point $C$ on the graph.
Equilibrium in the Long Run:
- Normal profits only: Due to the entry and exit of firms, abnormal profits/losses are eliminated.
- Allocative Efficiency: Achieved when $Price = Marginal Cost$ .
- Productive Efficiency: Achieved at the minimum point of the Average Cost ( $AC$ ) curve.
- Full Equation: $P = MR = MC = AC$ .

Adjustment from Short-Run to Long-Run

From Abnormal Profits to Normal Profits (Entry Effect):
- Economic profits attract newcomers.
- Entry of new firms increases industry supply.
- Industry supply curve shifts to the right.
- Market price falls from $P_1$ to $P_2$ until only normal profits (zero economic profits) are made.
From Losses to Normal Profits (Exit Effect):
- Sellers unable to cover Average Variable Cost ( $AVC$ ) or Total Variable Cost ( $TVC$ ) leave the market.
- Exit of firms leads to a decrease in market supply.
- Industry supply curve shifts to the left.
- Market price rises to $P_2$ until firms earn normal profits ( $P = AC$ ).

The Decision to Produce and Shut Down

Short Run Production Decision:
- A firm continues production as long as the Price ( $P$ ) is at least equal to the minimum Average Variable Cost ( $AVC$ ).
- A firm will continue to operate even if suffering losses, provided it covers its variable costs.
Shut Down Point:
- The point where $Price = \text{minimum } AVC$ .

Determining the Supply Curve

The Individual Firm Supply Curve:
- Short Run: The supply curve is the Marginal Cost ( $MC$ ) curve above the minimum point of the Average Variable Cost ( $AVC$ ).
- Long Run: The supply curve is the Marginal Cost ( $MC$ ) curve above the Average Cost ( $AC$ ) curve (price must cover all costs).
Industry Supply Curve Types:
- A horizontal long-run supply curve.
- An upward-sloping long-run supply curve.
- A downward-sloping long-run supply curve.

Active Learning and Key Review Points

Definitions Checklist:
- Normal profits: Price equals average cost ( $P = AC$ ).
- Break-even point: Price equals average cost ( $P = AC$ ).
- Shutdown point: Price equals average variable cost ( $P = AVC$ ).
- Abnormal profit: Price is greater than average cost (P > AC).
Truths about Perfect Competition:
- Firms are completely free to enter or leave the market.
- Firms are price takers (no individual control over price).
- Products are identical (not just similar).
- There is no need for advertising to shift demand curves, as the product is homogenous.
Summary Summary:
- Firms maximize profit where $P = MR = MC$ .
- Abnormal profits/losses only exist in the short run.
- Long-run ensures allocative and productive efficiency.

Questions & Discussion

How many firms are there in a perfectly competitive market?
- There are a very large number of firms.
Explain why firms in perfect competition are price takers.
- Because each firm is so small relative to the total market that its output decisions cannot influence the market price.
Can firms in perfect competition make abnormal profits?
- Yes, but only in the short run.
Explain why the absence of barriers to entry is an important assumption in perfect competition.
- It ensures that abnormal profits are competed away in the long run as new firms join the industry.
Why is the fact that firms offer homogeneous products an important assumption in perfect competition?
- It ensures that buyers have no preference for one seller over another, forcing firms to be price takers.
Explain what happens in the long run if a firm in a perfectly competitive market is making a loss.
- Firms will exit the industry, shifting supply to the left and raising the market price until normal profits are restored.
Is a firm in perfect competition allocatively efficient in the long run?
- Yes, because they produce where $P = MC$ .
Explain how the supply curve in perfect competition is derived.
- It is derived from the Marginal Cost curve (above the minimum $AVC$ in the short run).
Can firms in perfect competition ever make abnormal profits?
- Only in the short run; entry of new firms prevents this in the long run.
At what level of output do firms in perfect competition produce?
- They produce at the level where $MR = MC$ .