Excerpt from the Commission Notice "Guidelines on the assessment of horizontal
mergers under the EC Council Regulation on the control of concentrations between
undertakings"; Section III (Official Journal, C 31/03, 05.02.2004).
III. Market Share and Concentration Levels
- Market shares and concentration levels provide useful first indications of the
market structure and of the competitive importance of both the merging parties and their
- Normally, the Commission uses current market shares in its competitive analysis13.
However, current market shares may be adjusted to reflect reasonably certain future
changes, for instance in the light of exit, entry or expansion14. Post-merger market
are calculated on the assumption that the post-merger combined market share of the
merging parties is the sum of their pre-merger market shares15. Historic data may be
if market shares have been volatile, for instance when the market is characterised by
large, lumpy orders. Changes in historic market shares may provide useful
about the competitive process and the likely future importance of the various
for instance, by indicating whether firms have been gaining or losing market shares.
any event, the Commission interprets market shares in the light of likely market
conditions, for instance, if the market is highly dynamic in character and if the
structure is unstable due to innovation or growth16.
- The overall concentration level in a market may also provide useful information
about the competitive situation. In order to measure concentration levels, the Commission
often applies the Herfindahl-Hirschman Index (HHI)17. The HHI is calculated by summing
the squares of the individual market shares of all the firms in the market18. The HHI
gives proportionately greater weight to the market shares of the larger firms. Although it is
best to include all firms in the calculation, lack of information about very small firms
may not be important because such firms do not affect the HHI significantly. While
the absolute level of the HHI can give an initial indication of the competitive
pressure in the market post-merger, the change in the HHI (known as the "delta")
is a useful proxy for the change in concentration directly brought about by the
Market share levels
- According to well-established case law, very large market shares - 50% or more -
themselves be evidence of the existence of a dominant market position20. However,
smaller competitors may act as a sufficient constraining influence if, for example,
have the ability and incentive to increase their supplies. A merger involving a firm
market share will remain below 50% after the merger may also raise competition
concerns in view of other factors such as the strength and number of competitors, the
presence of capacity constraints or the extent to which the products of the merging
are close substitutes. The Commission has thus in several cases considered mergers
resulting in firms holding market shares between 40% and 50%21, and in some cases
below 40%22, to lead to the creation or the strengthening of a dominant position.
- Concentrations which, by reason of the limited market share of the undertakings
concerned, are not liable to impede effective competition may be presumed to be
compatible with the common market. Without prejudice to Articles 81 and 82 of the
Treaty, an indication to this effect exists, in particular, where the market share of the
undertakings concerned does not exceed 25%23 either in the common market or in a
substantial part of it24.
- The Commission is unlikely to identify horizontal competition concerns in a
market with a post-merger HHI below 1000. Such markets normally do not require extensive
- The Commission is also unlikely to identify horizontal competition concerns in a
merger with a post-merger HHI between 1000 and 2000 and a delta below 250, or a merger
with a post-merger HHI above 2000 and a delta below 150, except where special
circumstances such as, for instance, one or more of the following factors are present:
- a merger involves a potential entrant or a recent entrant with a small market
- one or more merging parties are important innovators in ways not reflected in
- there are significant cross-shareholdings among the market participants25;
- one of the merging firms is a maverick firm with a high likelihood of
disrupting coordinated conduct;
- indications of past or ongoing coordination, or facilitating practices, are
- one of the merging parties has a pre-merger market share of 50% of more26.
- Each of these HHI levels, in combination with the relevant deltas, may be used as an
initial indicator of the absence of competition concerns. However, they do not give
rise to a presumption of either the existence or the absence of such concerns.
13 As to the calculation of market shares, see also Commission Notice on the definition of
market for the purposes of Community competition law, 1997 OJ C 372/3, paragraphs
14 See e.g. Case COMP/M. 1806 - Astra Zeneca/Novartis, points 150 and 415.
15 When relevant, market shares may be adjusted, in particular, to account for controlling
interests in other
firms (See e.g. Case IV/M.1383 - Exxon/Mobil, points 446-458; Case
COMP/M. 1879 -
Boeing/Hughes, points 60-79; Case COMP/JV 55 - Hutchison/RCPM/ECT, points
66-75), or for other
arrangements with third parties (See, for instance, as regards sub-contractors,
2001/769/EC in Case COMP/M. 1940 - Framatome/Siemens/Cogema, OJ L 289,
6.11.2001, p.8, point
16 See, e.g. Case COMP/M. 2256 - Philips/Agilent Health Care Technologies, points 31-32,
COMP/M. 2609 - HP/Compaq, point 39.
17 See e.g. Case IV/M. 1365 - FCC/Vivendi, point 40; Case COMP/JV 55 -
50. If appropriate, the Commission may also use other concentration measures such as,
concentration ratios, which measure the aggregate market share of a small number
(usually three or
four) of the leading firms in a market.
18 For example, a market containing five firms with market shares of 40%, 20%, 15%, 15%,
respectively, has an HHI of 2550 (402 + 202 + 152 + 152 + 102 = 2550). The HHI ranges from
zero (in an atomistic market) to 10000 (in the case of a pure monopoly).
19 The increase in concentration as measured by the HHI can be calculated independently
of the overall
market concentration by doubling the product of the market shares of the merging firms. For
merger of two firms with market shares of 30% and 15% respectively would increase the HHI by
(30x15x2 = 900). The explanation for this technique is as follows: Before the merger, the market
of the merging firms contribute to the HHI by their squares individually: (a)2 + (b)2. After the
the contribution is the square of their sum: (a + b)2, which equals (a)2 + (b)2 + lab. The increase in
HHI is therefore represented by lab.
20 Case T-221/95, Endemol v Commission,  ECR 11-1299, paragraph 134, and Case
Gencor v Commission,  ECR 11-753, paragraph 205. It is a distinct question whether a
position is created or strengthened as a result of the merger.
21 See e.g. Case COMP/M. 2337 - Nestle/Ralston Purina, points 48-50.
22 See e.g. Commission Decision 1999/674/EC in Case IV/M. 1221 - Rewe/Meinl, OJ L 274,
p. 1, points 98-114; Case COMP/M.2337 - Nestle/Ralston Purina, points 44-47.
23 The calculation of market shares depends critically on market definition. It must be
emphasised that the
Commission does not necessarily accept the parties' proposed market definition.
24 Recital 32 of the Merger Regulation. However, such an indication does not apply to cases
proposed merger creates or strengthens a collective dominant position involving the
concerned" and other third parties (see Joined Cases C-68/94 and C-30/95, Kali & Salz, 
1375, paragraphs 171 et seq; and Case T-102/96, Gencor v Commission,  ECR 11-753,
paragraphs 134 et seq).
25 In markets with cross-shareholdings or joint ventures the Commission may use a
modified HHI, which
takes into account such share-holdings (see e.g. Case IV/M.1383 - Exxon / Mobil, point
26 See paragraph 17 above.