Warren Buffett is arguably the world’s most famous investor, and his investment moves are closely followed. Each quarter, the company he runs, Berkshire Hathaway, discloses its current holdings to shareholders.

In other words, history has shown that when Buffett's prized valuation tool moves well beyond the bounds of its long-term average, trouble follows for Wall Street. This may be why the Oracle of Omaha has been a net seller of stocks for eight consecutive quarters at Berkshire Hathaway, to the tune of $166.2 billion.