Facepalm. It's not an explicit contract in the sense of them coming to one table and agree with it, it's implicit in them having the common interest. Steve Keen

Facepalm. It's not an explicit contract in the sense of them coming to one table and agree with it, it's implicit in them having the common interest. Steve Keen did models where independent agents can become oligopolists even without any communication whatsoever, just by virtue of seeking maximal profit. There are many similar dynamical systems.