One should have a wide variety of assets in one's portfolio. And oil, by the way, is a particularly important asset to have in one's portfolio because we need it, and the economy thrives on it.

Fear causes individuals to restrain their spending and firms to withhold investments; as a result, the economy weakens, confirming their fear and leading them to restrain spending further. The downturn deepens, and a vicious circle of despair takes hold.

In a bubble, eventually people start saying, 'Wait a minute... these prices are way too high! What is anyone buying anymore? What could they possibly be thinking?' And then there's a correction and a bursting.

Robert J. Shiller Quotes