Self-fulfilling prophecy

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, 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.