netting factor

Hi, Page 65, R46.P2.T6. Gregory Notes it says that the netting factor is given by: netting factor = NF = sqrt(n + n*(n-1)*rho-bar)/n While I see that if rho-bar = 1 (no netting benefit) then NF = 100% and of rho-bar=0, then NF = 1/ sqrt (n), I do not see how NF can be 0% with perfect...