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> From the S&P web site:
>
> "The history of the S&P 500 dates back to 1923, when Standard and Poor's
> introduced an index covering 233 companies. The index, as it is known
> today, was introduced in 1957 when it was expanded to include 500
> companies."
Thanks Bob. So the data back to 1923 should be pretty good as S&P was
still picking the companies to include according to their criteria.
Their top 233 would represent most of the cap weighting of the 500 if
today's index is any indication.
I'm guessing that before 1923 they are just assuming the S&P tracked the
Dow. Or maybe they are tracking the original 233 companies backward
assuming (bad assumption) that there would be no changes in 50 years.
--
Dennis
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