Discussion on characteristics of companies in an oligopoly
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 companies worldwide), an executive for Perdue said: "It's an oligopoly. When one (company) changes price, they all do usually within minutes."
Why is it not surprising to find which in an oligopoly which sells a basically undifferentiated product like chicken growth hormone all the companies change prices simultaneously, even if there is no explicit price fixing?