Greenblatt wants this for the same reason that Graham wanted a company with Revenue over $100M- Big companies fail less frequently than smaller ones. Greenblatt also has a few other points to make in this respect:
small capitalization stocks did not appreciably outperform large caps
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for larger stocks (market caps over $1 billion) the results for the magic formula remain incredibly robust
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So basically go big because it works.
Greenblatt excluded Non US companies. The conclusion is based around the fact that some countries have loose regulations around investing. Greenblatt also seems to argue that there is no need to take on the additional risk if there are a sufficient number of American companies to invest in.
The final rule of excluding financial and utility companies is a bit confusing and is only addressed in a footnote:
Utilities, financial stocks and companies where we could not be certain that the information in the database was timely or complete were eliminated.
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So What Would Graham Think about these Rules?
Hope you enjoyed part two of the series. Drop me a line with your thoughts or questions and stay tuned for the next session where we will look further at some of the other criteria that Greenblatt put forward.
Be sure to check the previous parts in this series:
Part 1 Graham vs. Greenblatt (Session 1)