I have great respect for Jeremy Grantham and I must admit to ripping off his method of arriving at a fair value on the S&P 500 (approximately 900). Last quarter Jeremy Grantham decided to take a speculative long based on the "liquidity" trade. He just wanted to join the party. In hindsight, that was the canary in the coal mine. If even one of the biggest big picture bears turned positive, based on essentially "a feeling" than the market had sucked in everybody. Even the greats make mistakes and the stock market is a never ending learning process. His excellent quarterly piece is now available on the GMO website.