27. It is also not required for a finding of dominance that the undertaking in question has eliminated all opportunity for competition on the market.27 For Article 82 to apply it is not a condition that competition has been eliminated.28 On the other hand, the fact that an undertaking is compelled by the pressure of its competitors' price reductions to lower its own prices is in general incompatible with the independent conduct which is the hallmark of a dominant position. In that case the undertaking concerned is likely to be subject to effective competitive constraints, which is incompatible with the existence of substantial market power. 4.2. SINGLE DOMINANCE
“Power to behave to an appreciable extent independently of its competitors, its customers and ultimately of the consumers
28. When the relevant market has been defined, it can be analysed whether on that market the allegedly dominant undertaking “has the power to behave to an appreciable extent independently of its competitors, its customers and ultimately of the consumers”, that is, whether it holds substantial market power. In conducting this analysis it is relevant to consider in particular the market position of the allegedly dominant undertaking, the market position of competitors, barriers to expansion and entry, and the market position of buyers. The existence of a dominant position may derive from several factors which, taken separately, are not necessarily determinative.29 4.2.1 MARKET POSITION OF ALLEGEDLY DOMINANT UNDERTAKING AND ITS RIVALS
Market shares are first indication of dominance 29. The analysis of the market position of the allegedly dominant undertaking and its rivals provides insight into the degree of actual competition on the market. The starting point for this analysis is the market shares of the various players. Market shares provide useful first indications of the market structure and of the competitive importance of various undertakings active on the market. If the undertaking concerned has a high market share compared to other players on the market, it is an indication of dominance, provided that this market share has been held for some
See Case 27/76 United Brands, cited in footnote 5, paragraph 113, and Case T-395/94 Atlantic Container Line AB and Others v Commission  ECR II-875, paragraph 330. See paragraphs 91-92. Case 85/76 Hoffmann-La Roche, cited in footnote 5, paragraph 39.