The TAIEX compiled by TWSE is calculated by the following formula:
Index = Aggregate market value / Base value of the current day * 100
The aggregate market value is the aggregate of the market values obtained by multiplying the traded price of each constituent stock by the number of issued shares of the current day.
If there is no traded price on the current day, the opening auction reference price of the current day may be used for calculation. However, stock of newly listed companies included in calculation of the index may be accounted for on the basis of the number of listed shares of the current date.
The base value at the time of commencement of calculation of the index base period is the current aggregate market value at the time.