by word-of-mouth feedback loops, as initial rises in asset price attract new buyers and generate further inflation. The growth of the bubble is followed by a precipitous collapse fueled by the same phenomenon. Speculative bubbles are essentially social epidemics whose contagion is mediated by the structure of the market. Some economists link asset price movements within a bubble to fundamental economic factors such as cash flows and discount rates.

In 1936, John Maynard Keynes