HHI Explorer

The Herfindahl-Hirschman Index is the standard concentration measure antitrust regulators use (the US DOJ/FTC merger guidelines, for one): square every participant's share, then add them up. on a 0–10,000 scale. If one sector held 100% of the network, HHI = 100² = 10,000; split evenly across all 11 sectors, HHI = 11 × (100/11)² ≈ 909. The DOJ/FTC bands: below 1,500 is unconcentrated, 1,500–2,500 is moderately concentrated, above 2,500 is highly concentrated — this network's asset and liability HHI both sit in the 1,500–2,000 range across most of the sample, driven mainly by Banks.

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Squaring is what makes it a concentration measure rather than just a count: a sector twice as big contributes four times as much to the total, so HHI rewards evenness and penalizes dominance far more than a simple share or a naive count of participants would.

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Share HHI uses each sector's slice of the F038 network's own total. PageRank HHI uses topology centrality instead of raw size, so it concentrates around whichever sectors are most central, not necessarily biggest. Share total HHI uses each sector's share of its whole official balance sheet, not just the instruments this network tracks — see the companion Instrument Explorer for how much of a gap that is, by instrument and by sector.