An abbreviation of the Bombay Exchange Sensitive Index (Sensex) - the benchmark index of the Bombay Stock Exchange (BSE). It is composed of 30 of the largest and most actively-traded stocks on the BSE. Initially compiled in 1986, the Sensex is the oldest stock index in India.

Investopedia Says:
The index is calculated based on a free-float capitalization method when weighting the effect of a company on the index. This is a variation of the market cap method, but instead of using a company's outstanding shares it uses its float, or shares that are readily available for trading. The free-float method, therefore, does not include restricted stocks, such as those held by company insiders that can't be readily sold.

To find the free-float capitalization of a company, first find its market cap (number of outstanding shares x share price) then multiply its free-float factor. The free-float factor is determined by the percentage of floated shares to outstanding. For example, if a company has a float of 10 million shares and outstanding shares of 12 million, the percent of float to outstanding is 83%. A company with an 83% free float falls in the 80-85% free-float factor, or 0.85, which is then multiplied by its market cap (e.g., $120 million (12 million shares  x .$10/share) x 0.85 = $102 million free-float capitalization).

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