A self-fulfilling prophecy is a prediction that, in being made, actually causes itself to become true. For example, in the stock market, if it is widely believed that a crash is imminent, this may reduce confidence and actually cause such a crash. In short, because the prophecy was known, and was sufficiently credible, it affected people's actions and caused itself. Robert K. Merton is usually acknowledged as the maker of this phrase and using it in sociology. Another interesting example is Moore's Law in semiconductor industry.
