Indeed, the financial world is such that any insight is almost immediately used to trade for a profit. - Didier Sornette

In order to have a continuing influence, the stock market has to continue rising at an accelerating pace faster than exponential. Only a faster-than-exponential stock market growth makes private investors feel richer.

A bubble that goes up is just one that could have crashed but did not.

The assumption of perfectly rational, maximizing behavior won out until recently in the art of modeling, not because it often reflects reality, but because it was useful.