Interdependence in an Oligopoly

A firm selling into a market with a million anonymous buyers and dozens of competitors doesn't worry about any single buyer or rival changing its plans. An oligopoly is different. When only three or four airlines fly the same route, each one controls enough of the market that its pricing decision visibly moves the others' sales. So before setting a fare, a pricing manager has to guess what the rivals will do in response, and the rivals are doing the same thing about her. That back-and-forth guessing is strategic interdependence: no firm can choose a best price without thinking about the others' likely reactions.

This is why price wars start so easily. Say one airline quietly cuts its fare to pull in more passengers. Rivals watching their own bookings drop can't just absorb the loss, so they cut their fares too, often below the first firm's new price. The original firm, seeing its advantage erased, cuts again. Each round is a rational response to the last move, but the chain can drive fares down toward cost for everyone, with no firm better off than when it started.

It's tempting to picture an oligopoly as a monopoly cut into a few equal slices, each firm just quietly holding its piece. That misses the interdependence entirely. A monopolist sets its price once, with no rival to react to. Oligopoly firms never get that luxury. This sets up the next question: whether rivals can escape the price-war trap by cooperating instead, which is where collusion and cartel behavior come in.