My bad, but I think the study would have actually been less flawed with the Fortune 500. S&P are subjectively chosen "market leaders"; thus you not only get the

My bad, but I think the study would have actually been less flawed with the Fortune 500. S&P are subjectively chosen "market leaders"; thus you not only get the bias towards companies with large revenues, but also an opaque bias related to the committees non-transparent criteria.