HHI Calculator (Herfindahl-Hirschman Index)

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Market share as a percentage (e.g. 30 for 30%).
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Leave at 0 if the market has fewer than 6 firms.
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Share of one firm in a proposed merger. Both firms are replaced by a combined entity. Leave at 0 to skip merger analysis.
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Share of the other firm in the proposed merger.
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HHIModerately concentrated
2,250

Herfindahl-Hirschman Index (0 = perfect competition, 10,000 = monopoly)

Normalized HHI0.0313
Active firms5
Total share accounted for100%
Firm 1 contribution900
Firm 2 contribution625
Firm 3 contribution400
Firm 4 contribution225
Firm 5 contribution100
2,250 HHI
Unconcentrated<1500Moderate1500-2500Highly concentrated2500+

HHI is 2250, a moderately concentrated market.

  • The market is moderately concentrated under DOJ/FTC 2023 Merger Guidelines, indicating potential antitrust concern in some transactions.
  • 5 active firms account for 100.0% of the entered market share.
  • Normalized HHI is 0.0313, ranging from 0 (even split among 5 firms) to 1 (monopoly).

Next stepFor regulatory filings, use actual revenue or shipment data to calculate market shares rather than estimates.

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