Madoff's annual returns were "unusually consistent",[49] around 10%, and were a key factor in perpetuating the fraud.[50] Ponzi schemes typically pay returns of 20% or higher, and collapse quickly. One Madoff fund, which described its "strategy" as focusing on shares in the Standard & Poor's 100-stock index, reported a 10.5% annual return during the previous 17 years. Even at the end of November 2008, amid a general market collapse, the same fund reported that it was up 5.6%, while the same year-to-date total return on the S&P 500-stock index had been negative 38%.[14] An unnamed investor remarked, "The returns were just amazing and we trusted this guy for decades if you wanted to take money out, you always got your check in a few days. That's why we were all so stunned."[51][clarification needed][52]

The Swiss bank Union Bancaire Prive explained that because of Madoff's huge volume as a broker-dealer, the bank believed he had a perceived edge on the market because his trades were timed well, suggesting they believed he was front running.[53]

how long did the monthly average return last?