On Mon, 20 Apr 2009, Paar David wrote: It's calculated as per the account given on Wikipedia for "a population uniform on the values y_i, i = 1 to n, indexed in non-decreasing order (y_i <= y_{i+1})". That is, G = [(2 * sum(i * y_i)) / (n * sum(y_i))] - [(n + 1)/n] This is equivalent to the next formula given on Wikipedia, expressed in terms of a discrete probaility function f(y). Allin Cottrell