Market Share Distribution
0
HHI Score
Competitive
0
1,500 (Moderate)
2,500 (High)
10,000
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Select two firms to simulate a merger and see the HHI impact.
Firm Market Shares
Understanding HHI
The Herfindahl-Hirschman Index measures market concentration by summing the squares of each firm's market share percentage.
HHI = Σ(market share)² = s₁² + s₂² + ... + sₙ²
DOJ/FTC Guidelines:
• HHI < 1,500: Unconcentrated market
• HHI 1,500–2,500: Moderately concentrated
• HHI > 2,500: Highly concentrated
A merger that increases HHI by more than 200 points in a highly concentrated market is presumed likely to enhance market power.