The hhi belongs to a family of indices that also includes the rosenbluth index and the entropy index jacquemin. For example, suppose i have a firm with 10 shareholders, each holding the following percentage the total usually adds up to less than 100% as some are missing. The herfindahl index also known as herfindahlhirschman index, hhi, or sometimes hhiscore is a measure of the size of firms in relation to the industry and an indicator of the amount of competition among them. A evolucao da concentracao sectorial em portugal entre 1995 e 2006. This meaures how concentrated the ownership of a company is. A mathematical analysis of the hirfindahlhirschman index. This video shows how to calculate the hhi using several examples. Pdf hirschmanherfindahl index determination under incomplete. The term hhi means the herfindahlhirschman index, a commonly accepted measure of market concentration. The hhi is calculated by squaring the market share of each firm competing in the market and then summing the resulting numbers. It is calculated by squaring the market share of each firm competing in a market and then summing the. The herfindahlhirschman index hhi is a commonly accepted measure of market concentration. The herfindahl hirschman index hhi is a commonly accepted measure of market concentration. Hirschman, it is an economic concept widely applied in competition law, antitrust and also technology management.