Calculates the Herfindahl-Hirschman Index: HHI = Σ(market share)², used by antitrust regulators to assess market concentration. HHI < 1,500 is unconcentrated; 1,500–2,500 is moderate; > 2,500 is highly concentrated — US DOJ considers mergers in highly concentrated markets (ΔHHI > 200) presumptively anticompetitive.
Inputs
S1 Pct
Reference formula or conversion factor shown for context.
S2 Pct
Reference formula or conversion factor shown for context.
S3 Pct
Reference formula or conversion factor shown for context.
S4 Pct
Reference formula or conversion factor shown for context.
S5 Pct
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Results
HHI score
A numerical rating from the scoring model in use.
effective number of firms N_eff
Sample size or count used in the calculation.
4-firm concentration ratio CR4 (%)
The proportional relationship between two quantities.
total share captured (%)
The combined total across all inputs and components.
HHI = Σ(si²) where si = market share %
Reference formula or conversion factor shown for context.
market structure
Reference formula or conversion factor shown for context.