oligopoly

An oligopoly is a market dominated by just a few large firms — not one, not thousands, but a small club whose members all know each other's names. Think of the handful of companies that make most of the world's passenger jets, smartphones, or breakfast cereals, or the two or three supermarket chains that ring up most of a country's groceries. Because there are only a few players, each one is big enough to matter, and what one does ripples straight onto the others. The word comes from the Greek oligos (few) and polein (to sell).

The defining feature of oligopoly is interdependence: each firm's best move depends on what it expects its rivals to do. If a lone airline cuts fares it can grab market share — but only if rivals don't match; if they do, everyone just earns less on the same passengers. That mutual second-guessing makes oligopoly the natural home of game theory and gives it a famously unstable, knife-edge feel. The few firms are pulled in two directions at once: toward cooperation (quietly keeping prices high together, so all of them profit) and toward rivalry (each tempted to undercut the others to win customers). Which force wins shapes everything — sometimes you get cosy, comfortable prices that look almost monopolistic; sometimes a brutal price war that benefits customers and bleeds the firms.

Oligopoly is probably the most common structure for big, branded modern industries, which makes it enormously important and frustratingly hard to pin down — there is no single neat model, because the outcome hinges on how the rivals interact. It is also where competition authorities watch most nervously, because a few firms that recognise their shared interest can, without ever signing anything, drift into tacit collusion: matching each other's prices, following the leader, and quietly behaving like a single monopoly while looking like competitors.