Theblackswantheory was developed by Nassim Taleb to describe an event that is a complete surprise, has a major impact, and after the fact is rationalized with the benefit of hindsight.
Whether you are a devotee of theBlackSwanTheory or merely another hard-boiled cynic like me, you may now be counted among those who place little comfort in years of accumulated stock market statistics.
He calls them Black Swans, after the philosopher Karl Popper's observation that only a single blackswan is required to falsify thetheory that "all swans are white" even when there are thousands of white swans in evidence.