Résumé
This research aims to wonder about the bonds between competing aggressiveness and the exit of market. By the thorough study of a case, it shows how two firms deliberately eliminated from the market their two principal competitors to find themselves in situation of duopoly and, thus, to control the trend of prices to increase their performances. It also shows the processes of interdependence which make unstable the triopolies or quadriopolies, relative to the possibilities of stable and advantageous agreement in the duopolies.