Herfindahl-Hirschman Index - HHI

Definition of 'Herfindahl-Hirschman Index - HHI'


A commonly accepted measure of market concentration. It is calculated by squaring the market share of each firm competing in a market, and then summing the resulting numbers. The HHI number can range from close to zero to 10,000. The HHI is expressed as:

HHI = s1^2 + s2^2 + s3^2 + ... + sn^2 (where sn is the market share of the ith firm).

The closer a market is to being a monopoly, the higher the market's concentration (and the lower its competition). If, for example, there were only one firm in an industry, that firm would have 100% market share, and the HHI would equal 10,000 (100^2), indicating a monopoly. Or, if there were thousands of firms competing, each would have nearly 0% market share, and the HHI would be close to zero, indicating nearly perfect competition.

The U.S. Department of Justice uses the HHI for evaluating mergers.

Investopedia explains 'Herfindahl-Hirschman Index - HHI'


The U.S. Department of Justice considers a market with a result of less than 1,000 to be a competitive marketplace; a result of 1,000-1,800 to be a moderately concentrated marketplace; and a result of 1,800 or greater to be a highly concentrated marketplace. As a general rule, mergers that increase the HHI by more than 100 points in concentrated markets raise antitrust concerns.



comments powered by Disqus
Hot Definitions
  1. Benchmark Bond

    A bond that provides a standard against which the performance of other bonds can be measured. Government bonds are almost always used as benchmark bonds. Also referred to as "benchmark issue" or "bellwether issue".
  2. Market Capitalization

    The total dollar market value of all of a company's outstanding shares. Market capitalization is calculated by multiplying a company's shares outstanding by the current market price of one share. The investment community uses this figure to determine a company's size, as opposed to sales or total asset figures.
  3. Oil Reserves

    An estimate of the amount of crude oil located in a particular economic region. Oil reserves must have the potential of being extracted under current technological constraints. For example, if oil pools are located at unattainable depths, they would not be considered part of the nation's reserves.
  4. Joint Venture - JV

    A business arrangement in which two or more parties agree to pool their resources for the purpose of accomplishing a specific task. This task can be a new project or any other business activity. In a joint venture (JV), each of the participants is responsible for profits, losses and costs associated with it.
  5. Aggregate Risk

    The exposure of a bank, financial institution, or any type of major investor to foreign exchange contracts - both spot and forward - from a single counterparty or client. Aggregate risk in forex may also be defined as the total exposure of an entity to changes or fluctuations in currency rates.
  6. Organic Growth

    The growth rate that a company can achieve by increasing output and enhancing sales. This excludes any profits or growth acquired from takeovers, acquisitions or mergers. Takeovers, acquisitions and mergers do not bring about profits generated within the company, and are therefore not considered organic.
Trading Center