Herfindahl Index Rechner — Formel
## How to Calculate the Herfindahl-Hirschman Index
### Formula
**HHI = Sum of (si)^2**
where si is each firm's market share as a percentage. HHI ranges from near 0 (highly competitive) to 10,000 (monopoly with 100% share). US DOJ guidelines: HHI < 1,500 = unconcentrated, 1,500-2,500 = moderately concentrated, > 2,500 = highly concentrated.
### Formula
**HHI = Sum of (si)^2**
where si is each firm's market share as a percentage. HHI ranges from near 0 (highly competitive) to 10,000 (monopoly with 100% share). US DOJ guidelines: HHI < 1,500 = unconcentrated, 1,500-2,500 = moderately concentrated, > 2,500 = highly concentrated.
Lösungsbeispiel
Four firms with market shares: 40%, 30%, 20%, 10%.
- HHI = 40^2 + 30^2 + 20^2 + 10^2
- = 1600 + 900 + 400 + 100 = 3000
- HHI = 3000 (highly concentrated)
- Normalized = 3000 / 10000 = 0.30
- Equivalent equal-size firms = 10000/3000 ≈ 3.33