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The SEMDEX was launched at the inception of the SEM on 5th July 1989 with an index value of 100. SEMDEX was deemed to be an all share index designed to capture the price evolution of all the ordinary shares listed on the Official Market which met the SEM’s free-float requirements as defined in the listing rules of the Official Market. Since 12th September 2016, the SEMDEX (starting at its closing value on 9th September 2016) was converted into an index which tracks the price evolution of all rupee-denominated companies listed on the Official Market which meet the SEM’s free-float requirements.

The current value of SEMDEX is expressed in relation to a base value. The Index formula is as follows:

SEMDEX =          Current Market Value of  eligible rupee-denominated Ordinary Shares          x 100
                       Base Market Value of eligible rupee-denominated Ordinary Shares (Divisor)
Where, the market value of shares of a listed company is equal total number of ordinary shares issued times its closing market price.

Eligible Shares
To be eligible for inclusion in SEMDEX, a company must be incorporated in Mauritius or in an acceptable foreign jurisdiction.
Only ordinary shares that are listed and traded in MUR on the Official Market are included in the SEMDEX.
Where a company’s ordinary shares are issued partly paid and the call dates are already determined and known, the market price, for the purpose of calculating its market capitalisation, is adjusted so as to include all such calls (i.e., the fully paid price).

Only companies whose ordinary shares are listed and traded in MUR on the Official Market which meet the following free-float requirements of SEM will be included in the calculation of SEMDEX:

1.    Number of shareholders ----   200

2.    Market capitalisation of MUR 20 Million

3.    Percentage held in public  hands:

       •    25%

       •    15%, if the company undertakes to increase its shareholding to 20% by the 3rd year and 25% by the 5th year.

       •    10%, if the company has market capitalisation greater than MUR 2 Billion and undertakes to increase its shareholding to 20% by the 3rd year and 25% by the 5th year.

Divisor adjustments:

The key to the maintenance of the SEMDEX is the adjustment of the divisor.  Index maintenance, reflecting changes in shares outstanding, corporate actions, additional or removal of stocks to the index, should not change the level of SEMDEX.  Any change to the constituents of SEMDEX that alters the value of the index, while holding stock prices of the constituents constant, will require a divisor adjustment.

  = Divisor level Post corporate action
 = Divisor level prior to corporate action
= total market value post corporate action
= total market capitalisation prior to corporate action

Corporate action related changes: There is a large range of corporate action ranging from routine share issuances or buy backs to more complex events like spin-offs or mergers.  Some of these changes are listed below with notes about whether the divisor is adjusted.


Company added/deleted

Net change in market value determines the divisor adjustment.


Change in shares outstanding

Any combination of secondary issuance, share repurchase or buy back – share counts revised to reflect change.


Stock split

Share count revised to reflect new count. Divisor adjustment is not required since the share count and price changes are offsetting.



If the spun-off company is not being added to the index, the divisor adjustment reflects the decline in index market value (i.e., the value of the spun-off unit).



Spun-off company added to the index, no company removed from the index.


Spin off

Spun-off company added to the index, another company removed to keep number of name fixed. Divisor adjustment reflects deletion.


Special Dividend

When a company pays a special dividend the share price is assumed to drop by the amount of the dividend; the divisor adjustment reflects this drop in index market value.


Rights offering

Each shareholder receives the right to buy a proportional number of additional shares at a set (often discounted) price. The calculation assumes that the offering is fully subscribed. Divisor adjustment reflects increase in market cap measured as the shares issued multiplied by the price paid.


New Shares
If a constituent issued new shares in the current period which were not present in the previous period, the index algorithm adds newly issued capitalisation from total capitalisation in the current period.
A cancellation of shares by a constituent is treated as a negative new issue. Shares created by the conversion of other securities are treated as new issues.
Rights Issues
When shares begin trading ex-rights, the theoretical share price falls by the intrinsic value of the rights. Because the SEMDEX follows only the shares and not the rights, which may be traded separately, an adjustment is needed to prevent the index from dropping. The method is similar to that of a new issue. In both cases, the theoretical price is the weighted price of the shares at the instant after the change.
Dividend in Specie
Dividend in specie (in kind) means dividends not paid in cash. Such dividends are paid out in the form of assets / securities of companies owned by the issuer and are in a given amount.
Bonus Issues, Stock Splits and Reverse Splits
The number of shares created by the bonus issue or stock split is used to adjust the shares outstanding at the ex-bonus/split date. Similarly, a reverse split is recorded as a negative stock split while reducing the shares outstanding by the amount of the negative split. In the case of stock splits, as prices drop by the split ratio, total capitalisation does not change at the time of the split and no adjustment to the SEMDEX is needed. Stock dividends, also known as bonus issues, have the same effect as splits and no adjustment to the SEMDEX is therefore needed.
Cash Dividends
Cash dividends can affect share prices, but the industry norm is not to make any adjustment for such dividends in the SEMDEX. Cash dividends on a per share basis are recorded at the ex-dividend date, using gross cash dividends.
Suspension of Dealing
In the event that a security is suspended, the constituent may remain in the SEMDEX, at the price at which it is suspended, until suspension of dealing is removed.
Amalgamation (Merger), Restructuring or Takeovers
If an amalgamation (merger), Restructuring or Takeover results in one security being, absorbed by another constituent, the resulting company shall remain a constituent of the SEMDEX.
If a constituent company is taken over or absorbed by a non-constituent company, the original constituent shall be removed.
Adjustments for Corporate Actions
On Cum-date following close of Market the reference price of the security is adjusted to account for the Corporate Actions: Dividends, Rights Issue, Bonus Issue, Share Split, and Dividend in Specie. The Ex- reference price is adjusted to reflect its tick size as per the ATS Procedures. The price spread for the next session is based on the Ex- reference price.
Ex Dividend Ref Price = Cum Dividend Price – Amount of Dividend
Rights Issue
Ex-Rights Ref Price =

Bonus Issue
Ex-Bonus Ref Price =
                                  Cum-Bonus Price x Number of shares held as per ratio of Bonus Issue
                         Number of Shares held + Number of new shares receivable (as per ratio of Bonus Issue)
Share Split
Ex-Share Split Ref Price =     
                                              Cum-Share Split Price
                                                    Split factor

Dividend in Specie
Ex-Dividend in Specie Ref Price = Cum-Dividend in Specie Price – amount of Dividend in Specie
Increase in Share Capital.
Ex Ref Price = (Cum Share Price x No of Shares in Issue) + (New Shares x Issue Price)
                                         No of shares in Issue + No of New Shares

Decrease in Share Capital
Ex Ref Price =   Cum Share Price x No of Shares in Issue
                          No of Shares in Issue – Shares Cancelled
Determination of Right Price
Right price = Price of Security before trade date of Rights – Issue Price per share
Partly Paid Share
Partly Paid Share Price = Price of Security before trade date of partly paid share – Amount of call payment
Any other adjustment to the price of a security in respect of entitlements not mentioned above will be carried out based on international practice and standards and the market will be informed accordingly.