HHI market concentration classification
Find out which concentration band an HHI falls into: an HHI of 800 is competitive, below the 1500 threshold, while anything above 2500 counts as highly concentrated under the 2010 US merger guidelines. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Hhi
- 800
- Classification
- competitive
- Label
- Competitive (unconcentrated)
- Threshold moderate
- 1,500
- Threshold high
- 2,500
The Herfindahl-Hirschman Index is the workhorse summary of market concentration in antitrust screening, merger review, and industrial-organization homework. Analysts square each firm’s percentage market share, sum those squares, and obtain a single number between zero and ten thousand that rises as the industry becomes more top-heavy. This HHI market concentration classification tool takes that index and maps it onto the three standard US Department of Justice and Federal Trade Commission bands: competitive or unconcentrated markets when HHI is below one thousand five hundred, moderately concentrated markets from one thousand five hundred through two thousand five hundred, and highly concentrated markets above two thousand five hundred. You get a machine-readable classification code, a human label, the threshold constants, and the band bounds so legal notes, exam keys, and dashboards never disagree on which bucket a given HHI falls into.
What HHI measures and how the three antitrust bands work
Herfindahl-Hirschman Index equals the sum of the squares of each firm’s percentage market share in a defined product and geographic market. A pure monopoly with one hundred percent share scores ten thousand; fifty equal firms each holding two percent score two hundred; a duopoly of sixty and forty percent scores thirty-six hundred plus sixteen hundred, or fifty-two hundred. Antitrust agencies use fixed cut-points rather than continuous scores when they first screen a market or a proposed merger.
Under the 2010 US Horizontal Merger Guidelines still cited in classroom and practitioner materials, markets with HHI below one thousand five hundred are treated as unconcentrated (labeled competitive here), markets from one thousand five hundred through two thousand five hundred as moderately concentrated, and markets above two thousand five hundred as highly concentrated. Those labels do not by themselves approve or block a merger—agencies also look at delta-HHI, entry, and competitive effects—but they are the standard first cut that students, counsel, and product teams need in a deterministic form.
This capability does not recompute HHI from raw share tables; it classifies an already-computed index so every consumer of the same HHI agrees on the band.
Bands, boundary values and valid range
Boundary rules are intentional: HHI strictly less than one thousand five hundred is competitive; HHI from one thousand five hundred through two thousand five hundred inclusive is moderately concentrated; HHI strictly greater than two thousand five hundred is highly concentrated. Examples: eight hundred maps to competitive, one thousand eight hundred to moderately concentrated, three thousand two hundred to highly concentrated; exactly one thousand five hundred and exactly two thousand five hundred both sit in the moderate band.
Use the classification field in automation and the label field in user-facing copy so you never re-translate codes in every client.
Where HHI band classification earns its keep
Law-firm and agency checklists often need a one-line band for an already-computed HHI before deeper merger simulation work begins. Microeconomics and industrial-organization courses grade problems that ask whether a market is unconcentrated, moderately concentrated, or highly concentrated given a numeric HHI; a deterministic oracle removes spreadsheet threshold drift across graders. Pin the classification string in tests, reject values outside zero to ten thousand explicitly, and you get reproducible antitrust bands for homework, LMS plugins, and lightweight compliance notes without standing up a full econometrics stack.
What you can do with it
Merger screening checklists
Map a precomputed HHI to competitive, moderately concentrated, or highly concentrated bands before deeper delta-HHI and competitive-effects analysis.
IO homework and exam keys
Grade Herfindahl band questions with a deterministic oracle that applies the 1500/2500 thresholds the same way every time.
Market-structure dashboards
Label industry concentration cards from a stored HHI without hard-coding threshold constants in every front-end client.
FAQ
What HHI thresholds does this classifier use?
US DOJ/FTC Horizontal Merger Guidelines (2010): HHI below 1500 is competitive (unconcentrated), 1500–2500 is moderately concentrated, and above 2500 is highly concentrated.
What range is valid for hhi?
A finite number from 0 through 10000 inclusive, matching percentage-share HHI (sum of squared percent shares).
How are the boundary values 1500 and 2500 classified?
Strictly below 1500 is competitive; strictly above 2500 is highly concentrated.
Does this tool compute HHI from market shares?
No. It classifies an already-computed HHI. Compute sum of squared percentage shares elsewhere, then pass the index as hhi.
Does a highly concentrated result mean a merger will be blocked?
No. The bands are only a first screen. Agencies also look at how much a merger changes the HHI, how easily new firms can enter and the likely effects on competition before deciding.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/econ/hhi-market-classification \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"hhi":1800}'const res = await fetch("https://api.kit.forhosting.com/econ/hhi-market-classification", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"hhi": 1800
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/econ/hhi-market-classification",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"hhi": 1800
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/econ/hhi-market-classification", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"hhi":1800}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"hhi":1800}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/econ/hhi-market-classification", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"hhi": 1800
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "econ.hhi_market_classification",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
What HHI measures and how the three antitrust bands work
Because shares are percentages, the theoretical range is zero to ten thousand, which is the scale this endpoint accepts.
Input contract, response fields, boundaries, and errors
POST a JSON body with one required field: hhi, a finite number on the percentage-share scale from zero through ten thousand inclusive. Numeric strings are accepted; missing, empty, non-finite, or out-of-range values fail with invalid_input and are not billed. On success the body echoes hhi rounded for stable clients, classification as one of competitive, moderately_concentrated, or highly_concentrated, a short display label, threshold_moderate equal to one thousand five hundred, threshold_high equal to two thousand five hundred, band_low and band_high for the closed interval that contains the value, a guideline citation string naming the US DOJ/FTC Horizontal Merger Guidelines of 2010, and a compact formula string restating the three-way rule.
Where HHI band classification earns its keep
Market-structure dashboards and SEC-style industry briefs can call a tiny parse endpoint instead of hard-coding magic numbers that later diverge from the documented guideline. Content sites that rank for HHI market concentration classification benefit from a free browser tool whose math matches the paid API path on the shared pure module.
Technical questions
What does HHI market concentration classification cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.