time.30 If market shares have fluctuated significantly over time, it is an indication of effective competition. However, this is only true where fluctuations are caused by rivalry between undertakings on the market. Fluctuations caused, for instance, by mergers are not in themselves indicative of such rivalry.
Market shares, current or historic 30. Normally, the Commission uses current market shares in its competitive analysis.31
However, historic market shares may be used if market shares have been volatile, for instance when the market is characterised by large, lumpy orders. Changes in historic market shares may also provide useful information about the competitive process and the likely future importance of the 32various competitors, for instance, by indicating whether firms have been gaining or losing market shares. In any event, the Commission interprets market shares in the light of likely market conditions, for instance, whether the market is highly dynamic in character and whether the market structure is unstable due to innovation or growth.
Likely that very high market shares, which have been held for some time,
indicate a dominant position – fairly save harbour if market share not above 25% 31. It is very likely that very high markets shares, which have been held for some time,
indicate a dominant position.33 This would be the case where an undertaking holds 50 % or more of the market, provided that rivals hold a much smaller share of the market.34 In the case of
lower market shares, dominance is more likely to be found in the market share range of 40 % to 50 % than below 40 %, although also undertakings with market shares below 40 % could be
See Case 27/76 United Brands, cited in footnote 5, paragraph 111 and Case 85/76 Hoffmann-La Roche cited in footnote 5, paragraph 41. As to the calculation of market shares, see also Commission Notice on the definition of the relevant market, cited in footnote 11, paragraphs 54-55. See Case 85/76 Hoffmann-La Roche, cited in footnote 5, paragraph 41. See Case 85/76 Hoffmann-La Roche cited in footnote 5, paragraph 41; Case C-62/86 AKZO Chemie BV v Commission  ECR I-3359, paragraph 60, and Case T-395/94 Atlantic Container Line, cited in note 27, paragraph 328. See Case 27/76 United Brands, cited in footnote 5, paragraphs 108-109 where the undertaking concerned was found to be dominant with a market share between 40 % and 45 %. See also Case C-250/92, Gøttrup-Klim e.a. Grovvareforeninger v Dansk Landbrugs Grovvareselskab AmbA  ECR I-5641, paragraph 48, where the undertaking concerned held market shares of 36 % and 32 %, and the ECJ stated that an undertaking holding market shares of that size may, depending on the strength and number of its competitors, be considered to be in a dominant position.