"In addition to the Ranking Review, the securities in the Index are monitored every day by Nasdaq with respect to changes in total shares outstanding arising from secondary offerings, stock repurchases, conversions, or other corporate actions. Nasdaq has adopted the following weight adjustment procedures with respect to such changes. Changes in total shares outstanding arising from stock splits, stock dividends, or spin-offs are generally made to the Index on the evening prior to the effective date of such corporate action. If the change in total shares outstanding arising from other corporate actions is greater than or equal to 5.0%, the change will be made as soon as practicable, normally within ten (10) days of such action. Otherwise, if the change in total shares outstanding is less than 5%, then all such changes are accumulated and made effective at one time on a quarterly basis after the close of trading on the third Friday in each of March, June, September, and December. In either case, the Index share weights for such Index Securities are adjusted by the same percentage amount by which the total shares outstanding have changed in such Index Securities."
aj, I'm thinking that you need a paid subscription at Nasdaq to get this information. I found a site that showed the component weighting for the SPX and DOW, but it can no longer post info for the NDX (see bottom link). Anyway I found this --APPL is 13.25% and MSFT is 6.55%, (last paragraph of article).
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