About major usa market index?

Question

does anyone know when nasdaq, s&p, and DJ will update their list of companies? is there a set time or just when they feel like it, because i know the russell index is updating the companies that will be on and off their index next week

Answer 1

NASDAQ makes annual changes, effective the 3rd week of December.

Dow Jones makes changes from time to time "to adjust to the changing marketplace" with no set intervals.

S&P makes updates on a rolling basis with no set intervals.

Obviously, all the major indexes will make immediate changes in cases of mergers, spin-offs, and other irregular activity.