How do you measure the "sortedness" of a list? Here, I propose another measure for sortedness. The procedure is to sum the difference between the position of each element in the sorted list, x, and where it ends up in the unsorted list, f(x). We divide by the square of the length of the list and multiply by two, because this gives us a nice number between 0 and 1. Subtracting from 1 makes it range from 0, for completely unsorted, to 1, for completely sorted.