BackOligopoly and Game Theory: Microeconomics Study Notes
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Oligopoly: Market Structure and Characteristics
Definition and Key Features
An oligopoly is a market structure characterized by a small number of interdependent firms that dominate the market. Unlike perfect competition or monopoly, oligopolies require unique analytical tools due to the strategic interactions among firms.
Interdependence: Firms are large enough that their actions affect one another's profits and strategies.
Barriers to Entry: Significant obstacles prevent new firms from entering and competing away profits.
Measuring Market Concentration
The four-firm concentration ratio is a common tool for identifying oligopolies. It measures the percentage of industry sales accounted for by the four largest firms. A ratio above 40% typically indicates an oligopoly.
Industry | Four-Firm Concentration Ratio |
|---|---|
Warehouse clubs and supercenters | 94% |
Cigarettes | 91% |
Aircraft | 90% |
Breakfast cereal | 82% |
Automobiles | 58% |
Additional info: These ratios are calculated for national markets and may not account for foreign competition or local market variations.
Barriers to Entry in Oligopoly
Economies of Scale: When long-run average costs decrease as output increases, large firms have a cost advantage, making entry difficult for new, smaller firms.
Ownership of Key Inputs: Control over essential resources (e.g., bauxite for aluminum, diamonds, cranberries) can restrict entry.
Government-Imposed Barriers: Patents, occupational licensing, tariffs, and quotas can legally restrict entry.
Game Theory and Oligopoly Behavior
Introduction to Game Theory
Game theory is the study of strategic decision-making where the outcome for each participant depends on the actions of others. In oligopoly, firms use game theory to anticipate rivals' responses and maximize profits.
Rules: Define allowable actions (e.g., pricing, output levels).
Strategies: Plans of action to achieve objectives (e.g., maximize profit).
Payoffs: Outcomes resulting from the combination of strategies (e.g., profits).
Payoff Matrix and Dominant Strategies
A payoff matrix displays the profits for each firm under different strategy combinations. A dominant strategy is the best action for a firm, regardless of what the other firm does.
Example: In the streaming music market, both Spotify and Apple can choose to charge $14.99 or $9.99. The matrix shows the profits for each combination of choices.
Finding Dominant Strategies
For Spotify, charging $9.99 yields higher profit regardless of Apple's choice. Similarly, $9.99 is also the dominant strategy for Apple.
Nash Equilibrium
A Nash equilibrium occurs when each firm chooses the best strategy given the other's choice. In this example, both firms charging $9.99 is the Nash equilibrium.
Firms do not need dominant strategies for a Nash equilibrium to exist; they only need to be making the best response to each other.
Collusion and Cooperative Equilibrium
Firms could earn higher profits by colluding (agreeing to charge higher prices), but such agreements are illegal in many countries.
Noncooperative equilibrium: Firms act independently and pursue their own interests (Nash equilibrium).
Cooperative equilibrium: Firms coordinate actions to increase mutual payoffs (collusion).
The Prisoner's Dilemma
The prisoner's dilemma is a game where pursuing dominant strategies leads to a worse outcome for all players than if they had cooperated. In oligopoly, this often results in lower profits due to competitive pricing, even though collusion would be more profitable.
Repeated Games and Enforcement Mechanisms
Repeated Games and Price Matching
When games are repeated, firms can use strategies like price match guarantees to discourage price competition and avoid the low-profit Nash equilibrium.
Price match guarantees act as enforcement mechanisms, making it less attractive for firms to undercut each other.
Another method is price leadership, where one firm sets the price and others follow, leading to implicit collusion.
Cartels and Real-World Applications
Cartels and Collusion
A cartel is a group of firms that collude to restrict output and raise prices. The Organization of Petroleum Exporting Countries (OPEC) is a well-known example, though maintaining collusion is challenging over time.
Cartels with Unequal Members
When cartel members differ in size or cost structure, their incentives to cooperate may diverge, making collusion unstable.
Dominant strategies may lead some members to defect, undermining the cartel.
Sequential Games and Business Strategy
Sequential Games and Decision Trees
In sequential games, firms make decisions one after another, not simultaneously. These are analyzed using decision trees, which map out choices and payoffs at each stage.
Firms can use strategies like limit pricing to deter entry by potential competitors.
Bargaining Games and Subgame-Perfect Equilibrium
In bargaining situations, firms anticipate each other's responses. A subgame-perfect equilibrium is an outcome where no player can improve their result by changing their strategy at any stage.
Industry Competition: The Five Competitive Forces Model
Porter's Five Forces
Michael Porter's model identifies five forces that shape competition in an industry:
Competition from existing firms (e.g., SAT vs. ACT)
Threat from new entrants (e.g., Apple deterring Dell)
Competition from substitutes (e.g., digital encyclopedias replacing printed sets)
Bargaining power of buyers (e.g., Walmart negotiating lower prices)
Bargaining power of suppliers (e.g., Microsoft's pricing power as a dominant OS provider)
Firm Longevity and Market Dynamics
Even large firms are not immune to competition, technological change, and market evolution. Most large firms do not survive indefinitely due to these competitive pressures.
Additional info: Of the 1955 Fortune 500, only 53 remain on the list today, illustrating the dynamic nature of markets.
