Page "Ponzi scheme" Paragraph 9

Promoters also try to minimize withdrawals by offering new plans to investors, often where money is frozen for a longer period of time, in exchange for higher returns.

The promoter sees new cash flows as investors are told they could not transfer money from the first plan to the second.

If a few investors do wish to withdraw their money in accordance with the terms allowed, the requests are usually promptly processed, which gives the illusion to all other investors that the fund is solvent.