The financial year 1983-84 has been chosen as the base year. The price stability during that year and proximity to the index series were the main consideration for choice of 1983-84 as the base year.

The basic method of compilation is the same as the one used in the case of the BSE Sensitive Index. However, in the case of BSE National Index, a distinction is made between "local scrips" for which prices were taken from only one exchange and "Inter-Exchange scrips" for which an average of the prices quoted on two or more exchanges were considered for index compilation. .

Designation of the BSE 100 National Index to the BSE 100 Index As noted above, the BSE 100 National index used to take prices of certain scrips from other exchanges or weighted average of some scrips which were popular on other exchanges in order to reflect market movements at the national level. However, changes in trading technology, longer trading period and almost instantaneous availability of information across the country have ensured that there is little or no difference in prices of the index scrips. Therefore, the Exchange administration has decided to redesignate the BSE 100 National index as the 'BSE 100' index. Since October 14, 1996, the prices of the BSE are taken to calculate the index. .