Investors should be skeptical of history-based models. Constructed by a nerdy-sounding priesthood using esoteric terms such as beta, gamma, sigma and the like, these models tend to look impressive. Too often, though, investors forget to examine the assumptions behind the models. Beware of geeks bearing formulas.
Warren BuffettAnd people really behaved in a fraudulent way or something, we'll go back and find the culprits later on. But that really isn't the problem we have. I mean that's where it came from, though. We leveraged up and if you have a 20 percent fall in value of a $20 trillion asset, that's $4 trillion. And when $4 trillion lands - losses land in the wrong part of this economy, it can gum up the whole place.
Warren Buffett