The concept of a random walk is simple but rich for its many applications, not only in finance but also in physics and the description of natural phe… - 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.

These rumors do not circulate in all directions, but essentially from the top to the bottom of society. The rather sophisticated presentations, the apparently serious references that seem to justify their origins, and their distinguished proponents provide food for amplifications serving diverse interests and psychological biases in all layers of society.

Knowledge is encoded in models. Models are synthetic sets of rules, and pictures, and algorithms providing us with useful representations of the world of our perceptions and of their patterns.