Jeremy Grantham of GMO says there are two good standards for a bubble. One is boring statistics, and the other is an exciting behavioural frenzy, on which so many good books have been written. And based on the boring statistics, the data is really very clear: We are not even that close to a bubble. With the S&P 500 at around 1860 recently, we are at about a 1.4- to 1.5-sigma event. Another way to say that is that we are between one and two standard deviations outside the normal distribution of stock-valuation levels. A two-sigma event would put the S&P 500 at 2350. So using the standard definition, it has to go up another 30% from here to get to a bubble. But you don't know when an ordinary market move is a bubble; you only know that in hindsight. Read More: (VIEW LINK)