Testifying at a price fixing trial involving Cargill Corp. and the market for chicken growth hormone, (in which the Cargill is one of only three firms worldwide), an executive for Perdue said: "It's an oligopoly. When one (firm) changes price, they all do…Usually within minutes."
Why is it not surprising to find that in an oligopoly, which sells a basically undifferentiated product like chicken growth hormone all the firms change prices simultaneously, even if there is no explicit price fixing?