<human>:  When did the Ponzi scheme perpetrated by Bernie madoff start?
<bot>: The scheme started in the late 1990s. Bernie madoff was a financier who ran a Ponzi scheme. A Ponzi scheme is a fraudulent investment scheme in which money is paid to investors from their own money or the money of new investors. The scheme is named after Charles Ponzi, who was a famous swindler who ran a similar scheme in the 1920s.