AP Syllabus focus: ‘Governments use antitrust policy to make markets more competitive.’
Antitrust policy explains how governments preserve competition by limiting market power, blocking harmful mergers, and punishing collusion. It focuses on market performance: prices, output, innovation, and consumer welfare.
What antitrust policy is trying to fix
Markets can become less competitive when firms gain market power and can profitably raise price above competitive levels, restrict output, or reduce quality. Antitrust aims to move outcomes closer to competitive results by changing firm behavior or market structure.
Core idea: competition as a policy goal
Antitrust policy: Government enforcement of laws that promote competition by restricting anti-competitive conduct and limiting mergers or market structures that substantially reduce competition.
A more competitive market typically has:
Lower prices and higher quantities than monopoly-like outcomes
More pressure to innovate and cut costs
Less persistent economic profit from barriers to entry
Main antitrust tools used by governments
Antitrust enforcement usually targets three areas: collusion, single-firm exclusionary conduct, and mergers.
1) Collusion and cartels
Collusion occurs when firms coordinate to act like a monopoly (for example, agreeing on prices, output, or market division).
A payoff matrix for a collusive duopoly game ("cheat" versus "don’t cheat") illustrates the core incentive problem behind cartel instability. Even when joint profits are highest under cooperation, each firm can often raise its own payoff by deviating, making collusion hard to sustain without enforcement or repeated-game discipline. Source
Cartel: A group of firms that explicitly agree to coordinate prices, output, or other competitive decisions to increase joint profits.
Governments increase competition by:
Investigating communication and agreements among rivals
Imposing fines, damages, and sometimes criminal penalties on executives
Using leniency policies to encourage whistleblowing and destabilize cartels
2) Monopolization and exclusionary practices
Even without explicit collusion, a dominant firm may reduce competition through exclusionary conduct (strategies that make it harder for rivals to enter or expand). Enforcers look for behavior that harms competition, not merely aggressive rivalry.
Common issues include:
Predatory pricing claims (pricing below cost to drive rivals out, then raising prices)
Exclusive dealing or loyalty discounts that foreclose rivals from distribution
Refusals to deal or discriminatory access to essential platforms (case-dependent)
3) Merger policy (preventing harmful consolidation)
Merger: The combination of two firms into a single firm, potentially increasing market concentration and market power.
Agencies review whether a merger is likely to:
Raise prices or reduce output/quality
Facilitate collusion by reducing the number of competitors
Eliminate a close competitor (“head-to-head” rivalry)
A common screening metric is market concentration.
= Firm market share in percent
Higher HHI and a large increase in HHI after a merger can signal less competition, especially when entry is difficult.
Remedies: how competition is restored
If enforcement finds substantial harm to competition, governments may:
Block the merger
Require divestiture (sell assets/business lines to preserve rivalry)
Impose conduct remedies (rules limiting anti-competitive behavior)
In extreme cases, pursue breakups or ongoing oversight
Limits and trade-offs in antitrust enforcement
Antitrust decisions require judgement because:
Some large firms are efficient due to economies of scale, not anti-competitive behavior
Some conduct that hurts rivals can still benefit consumers (harder cases)
Defining the “relevant market” (product and geographic scope) can change conclusions
Enforcement errors matter: under-enforcement can allow durable market power; over-enforcement can discourage efficient growth and innovation
FAQ
They assess which products are close substitutes and the geographic area where firms compete.
A narrower market definition usually implies higher concentration and stronger market power concerns.
Structural remedies change the market structure (e.g., divestitures, breakups).
Behavioural remedies restrict conduct (e.g., non-discrimination rules, banning exclusivity), often requiring monitoring.
Vertical mergers don’t directly remove a rival, but may enable foreclosure (blocking rivals’ access to inputs or customers).
Authorities focus on incentive and ability to foreclose, plus efficiency claims.
They offer reduced penalties to the first cartel member to provide evidence.
This raises distrust within cartels and increases the probability of detection, making collusion harder to sustain.
Legal standards, evidentiary burdens, and policy goals vary.
Some jurisdictions prioritise consumer prices; others weigh fairness, market openness, or strategic industries more heavily.
Practice Questions
(2 marks) Explain one way antitrust policy can make markets more competitive.
1 mark: Identifies a valid antitrust action (e.g., blocking a merger, fining a cartel, requiring divestiture).
1 mark: Explains how it increases competition (e.g., prevents higher concentration, reduces collusion, enables entry/expansion, lowers prices/increases output).
(6 marks) A competition authority is reviewing a proposed merger between two of the four largest firms in a market with high barriers to entry. Discuss why the authority might challenge the merger and one remedy it could impose.
Up to 2 marks: Explains that fewer firms can increase market power/raise prices/reduce output or quality.
Up to 2 marks: Explains how high entry barriers make anti-competitive effects more likely/persistent (new rivals unlikely to enter and discipline prices).
1 mark: Identifies a relevant concern such as increased likelihood of collusion or loss of close competition.
1 mark: Proposes a remedy and links it to competition (e.g., block merger; divest assets to keep a competitor; conduct conditions to prevent foreclosure).
