There is growing consensus among Wall Street analysts that the relentless bull market rally in the S&P 500 Index (SP500) is simply unsustainable, and that investors face the imminent risk of a sharp reversal. Such bearish warnings offered by the financial media must have become so familiar to readers that they are beginning to sound like mere complaints rather than professional investment advice. And one can't help but wonder why the consensus has so often been caught on the wrong side of the market. Why do professional investment advisors and portfolio managers regularly misjudge market behaviour?