The even easier version (doesn't factor in the current shift): Check how many open shifts currently have 0 blocks. Multiply that by shift length (4 billion as of my previous post, 4.5 billion going forward), and compare that number to network diff.
At the risk of looking like a complete idiot, I'll ask this...
So, if the current network difficulty is 3,815,723,799, and with ZERO variance, how do you compute the number of shares it should take to find a block (is it just the network difficultly number)? Asked another way, what math do you use to to see if you are above or below 100%, on your "luck chart"?