The SENSEX comprises the 30 top companies from different sectors to create an unbiased index. The selection uses the following criteria.
The stocks of the company must trade for every day for one year
The company must belong to the top 150 companies listed based on the average number of trade (both buying and selling) and the average value of trade
The listing should be more than a year old
There are some preconditioning and exclusion criteria, like Z category companies and IPOs aren’t considered for inclusion. Also, the inclusion process requires companies to report their sales turnover for at least four quarters.