寡占とその不公正な慣行

Collusion occurs when firms in an oligopoly secretly agree to work together instead of competing, often leading to higher prices and less choice for consumers. For example, major oil-producing nations work together through OPEC to control oil prices. This practice undermines fair competition and harms consumer welfare by reducing market efficiency.

Price-fixing involves firms agreeing to sell at a set price above competitive equilibrium, acting as a joint monopoly. Predatory pricing, conversely, involves setting prices below average variable cost to drive competitors out of the market. The LCD panel case exemplified price-fixing, while Uber's dispute with Flywheel demonstrated predatory pricing tactics.

Market division occurs when competitors agree to divide territories to reduce competition, with each firm behaving as a local monopoly. The airline industry demonstrates this practice, where carriers manipulate routes and prices within assigned regions. This strategy allows firms to maintain higher prices and limit consumer choice within their designated areas.

Product tying happens when a company with market power for one product sells that product conditional on purchasing another product for which it lacks market power. Microsoft's inclusion of Internet Explorer with Windows exemplifies this practice. Tying can limit consumer choice and reduce market competitiveness by leveraging dominance from one market to another.

Output restrictions artificially inflate prices by limiting supply in oligopolistic markets. When firms collectively reduce production, they create scarcity that supports higher prices without explicit price agreements. This practice, combined with collusion, allows oligopolies to behave similarly to monopolies while maintaining the appearance of independent competition.

Bid rigging involves firms colluding to determine the winner of a public tender process, undermining the competitive bidding mechanism. Participating firms agree in advance on who will win and at what price, eliminating genuine competition. This practice harms consumers and taxpayers by inflating costs and reducing the benefits of open competitive procurement.

Public policy under oligopoly antitrust laws aims to preserve competitive markets by prohibiting collusion, price-fixing, and predatory practices. Regulators enforce these rules to protect consumer welfare and market efficiency. Consumer advocacy for fair competition also influences market practices, encouraging firms to compete legitimately rather than engage in anticompetitive conduct.