The EU authorities traditionally consider that there can be no restriction on a market where competition is already eliminated entirely independently of the action of the participants in an agreement. The absence of actual or potential competition on a market may be due to the existence of a de facto or de jure monopoly. However, the absence of a legal monopoly does not mean that there exists competition capable of being restricted; the possibility must be real and concrete and not merely abstract and theoretical for undertakings to compete with each other or for a new entrant to penetrate the market and compete with the established undertakings. However, it is not necessary to demonstrate with certainty that the undertaking would have entered the market and that that entry would inevitably have been successful.