What are the 4 important concepts of oligopoly?

1. Conjectural variation: each firm makes assumptions on the actions rival firms take in response to the firm’s own actions 2. Interdependence: each firm’s action depends on what it thinks about what actions the other firms will take 3. Collusion: can arise when two or more rival firms recognize the interdependence of their actions  might lead to formulation of joint action 4. Independent action: firm acknowledges that actions are interdependent but reaches conclusion that taking a unilateral decision is better for her (not contacting rivals)