It is amazing in 2012 that we still assume that all stress is bad -- it is disturbing that management "stories" are still so filled with misleading information. One could argue (notice "could") that the real problem here is the 11% "low" stress level -- not enough stress to perform well.
"Two-out-of-three people say the stress level in their workplace is high, according to a survey of more than 450 North American employees by Right Management, the talent and career management experts within ManpowerGroup."