Why do companies bring back added to the s&p 500?

Is it because of size? As CBG will be added and FSH will be dropped, but FSH is almost twice as big as CBG?
Answers:

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There are no set rules. The S&P Index Committee has the final speak based on their own criteria. If you want the full explanation, it is here:

http://www.ifa.com/media/images/pdf%20fi...

It is an unforced read.

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Its more about their revenue than the number of emplyees. Standard and Poors select the companies for that index. Go to their website for more info.

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