Q.1.What is SENSEX?
The SENSEX is a "Market Capitalization-Weighted" index of 30 stocks on Bombay stock exchange.
Bombay Stock Exchange Limited is the oldest stock exchange in Asia with a rich heritage. Popularly known as "BSE". The SENSEX is the benchmark index of the Indian Capital Markets with wide acceptance among individual investors, institutional investors, foreign investors and fund managers. Institutional investors, money managers and small investors all refer to the SENSEX for their specific purposes.
Q.2 How is SENSEX calculated?
SENSEX is calculated using a "Market Capitalization-Weighted" methodology. As per this methodology, the level of index at any point of time reflects the total market value of 30 component stocks relative to a base period. The base period of SENSEX is 1978-79. The actual total market value of the stocks in the Index during the base period has been set equal to an indexed value of 100. This is often indicated by the notation 1978-79=100.
The calculation of SENSEX involves dividing the total market capitalization of 30 companies in the Index by a number called the Index Divisor. The Divisor is the only link to the original base period value of the SENSEX. It keeps the Index comparable over time and is the adjustment point for all Index maintenance adjustments.
During market hours, prices of the index scrips, at which latest trades are executed, are used by the trading system to calculate SENSEX every 15 seconds and disseminated in real time.
Q.3 How is the closing Index calculated?
The closing SENSEX is computed taking the weighted average of all the trades on SENSEX constituents in the last 15 minutes of trading session. If a SENSEX constituent has not traded in the last 15 minutes, the last traded price is taken for computation of the Index closure. If a SENSEX constituent has not traded at all in a day, then its last day's closing price is taken for computation of Index closure. The use of Index Closure Algorithm prevents any intentional manipulation of the closing index value.
Q.4 How are adjustments for Bonus, Rights and newly issued Capital carried out in SENSEX?
I have come across this question many times and did some research to find out how it is done actually. The arithmetic calculation involved in calculating SENSEX is simple, but problem arises when one of the component stocks pays a bonus or issues rights shares. The Index Cell of the Exchange periodically adjusts the base value to take care of such corporate announcements.
Adjustments for Rights Issues:
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When a company, included in the compilation of the index, issues right shares, the market capitalisation of that company is increased by the number of additional shares issued based on the theoretical (ex-right) price. An offsetting or proportionate adjustment is then made to the Base Market Capitalisation (see ' Base Market Capitalisation Adjustment' below).
Adjustments for Bonus Issue:
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When a company, included in the compilation of the index, issues bonus shares, the market capitalisation of that company does not undergo any change. Therefore, there is no change in the Base Market Capitalisation, only the 'number of shares' in the formula is updated.
Other Issues:
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Base Market Capitalisation Adjustment is required when new shares are issued by way of conversion of debentures, mergers, spin-offs etc. or when equity is reduced by way of buy-back of shares, corporate restructuring etc.
Base Market Capitalisation Adjustment:
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The formula for adjusting the Base Market Capitalisation is as follows:
New Base Market Capitalisation = Old Base Market Capitalisation * (New Market Capitalisation/Old Market Capitalisation)
To illustrate, suppose a company issues right shares which increases the market capitalisation of the shares of that company by say, Rs.100 crores. The existing Base Market Capitalisation (Old Base Market Capitalisation), say, is Rs.450 crores and the aggregate market capitalisation of all the shares included in the index before the right issue is made is, say Rs.4781 crores. The "New Base Market Capitalisation " will then be = 450 X (4781+100)/4781
This new figure will be used as the Base Market Capitalisation for calculating the index number from then onwards till the next base change becomes necessary.