A Ponzi scheme is a fraudulent investment scheme that pays returns to separate investors from their own money or money paid by subsequent investors, rather than from any actual profit earned. The Ponzi scheme usually entices new investors by offering return other investments cannot guarantee, in the form of short-term returns that are abnormally high. The perpetuation of the returns that a Ponzi scheme advertises and pays requires an ever-increasing flow of money from investors to keep the scheme going.

The system is destined to collapse because the earnings, if any, are less than the payments. Usually, the scheme is interrupted by legal authorities before it collapses because a Ponzi scheme is suspected or because the promoter is selling unregistered securities. As more investors become involved, the likelihood of the scheme coming to the attention of authorities increases. While the system eventually will collapse under its own weight, the recent example of Bernard Madoff powerfully illustrates the ability of a Ponzi scheme to delude both individual and institutional investors as well as securities authorities for long periods.