A group of elderly women from Beardstown, Ill. caused a stir in the mid-'90s when they claimed their club, founded in 1983, had realized an annual return of more than 23% on their investments. The book they published, "The Beardstown Ladies' Common-Sense Investment Guide," became a New York Times best-seller.
But the folksy know-how of the group proved too good to be true and the impressive numbers attributable to mathematical errors. The group checked its 23% number with an auditor who
discovered the return was really 9.1%, well under the Standard & Poor 500's record average at the time. Turns out, one of the basic requirements of getting returns like Buffett is
doing the math right.